Twincest



"Twincest is wincest!"

Popular culture often expects twins to share everything, including, it seems, their beds. It's a particularly common trope in Slash Fic, Hentai, and porn, though it does occur in mainstream fiction often enough to be a discernible trope. It's especially common as a way of making Creepy Twins just that much more disturbing.

Note that Twincest is not necessarily homosexual: that's what fraternal and Half-Identical Twins are for. However, a great deal of the appeal to viewers is the popular fantasy of sleeping with two identical copies of a single hot person at the same time, so homosexual (or bisexual if there's a lucky third party of another gender) twincest is more often used to titillate viewers. For Yuri Fans and Yaoi Fans who became fans at least partly because they see a forbidden appeal to such relationships, Twincest supercharges that part of the appeal.

A common twist, in this and in Brother-Sister Incest in general, is for a couple to fall in love, only to find out later that they were Separated at Birth. (See genetic sexual attraction.) How far their relationship goes before they discover this generally depends on whether the plotline is supposed to be humorous or tragic.

It goes without saying that most Real Life twins are as completely repulsed by the idea as any other incest trope.

An old Japanese myth says that if two star-crossed lovers commit dual suicide, they get reincarnated as twins. This may be one of the factors in the frequency of Twincest stories in Anime.

Of course, sometimes even Twincest isn't quite incestuous enough for the writers.

Can overlap with a Twin Threesome Fantasy.

Anime and Manga

 * This is the main "schtick" of Hikaru and Kaoru from Ouran High School Host Club: making the club's female clients swoon and sigh over "the forbidden love between brothers!!!11!!!" Whether it's a put-on or not is hard to tell, given their trickster personalities.
 * Also deconstructed, as the twins are revealed to be dangerously codependent. This eventually sparks a feud between them, and they eventually learn how to be individuals.
 * Candy Boy is entirely about yuri twincest, in that Yukino does like to tease her sister Kanade quite a bit. There's nothing explicit going on, since Kanade decides to keep a cool outer appearance, although she is obviously enamored with her sister.
 * They kiss in the last non-DVD episode.
 * The manga
 * Black Lagoon's Hansel and Gretel. Given their history, this is possibly the least disturbing thing about them.
 * Shoujo Sect absolutely defines this trope with the Kasagi twins Aki and Nori. Just read their description in the manga itself.
 * Subverted in Gundam Seed: Kira and his Separated at Birth twin sister Cagalli meet in the first episode (neither knowing they're related), and when they reunite further in the series, Cagalli comforts the emotionally ragged Kira in a purely platonic way. This is ironically taken as a threat by Flay, Kira's screwed-up girlfriend (it's not a healthy relationship), despite the fact there's no romantic attraction to it. Further toyed with when Cagalli displays a Luminescent Blush at overhearing Flay admit to her ex-fiance Ssigh that she and Kira have slept together, and when Kira's adoptive parents (who are aware of Cagalli's identity) show a bit of alarm when Cagalli hugs Kira goodbye.
 * They're supposed to be Homage to Luke and Leia below, so yeah.
 * Mobile Suit Gundam 00 plays with this too. Whether Ribbons Almark and his "sister" Hilling Care qualify as twins is debatable,, but Healing seems to show a bit more adoration than is platonic towards Ribbons.
 * .hack//tasogare no udewa densetsu hints strongly at incest, or at least lust, between two characters who are twins. This is basically a Flanderization of subtler jokes in the manga, where it was the sister's completely different-looking and skimpily-dressed computer avatar that set off the whole thing. The anime altered the storyline near the end where their relationship is implied to be much stronger.
 * In Revolutionary Girl Utena, Half-Identical Twins Miki and Kozue have a bizarre relationship which may involve twincest, particularly in the movie.
 * Miki isn't sexually attracted to Kozue per se, but rather, he finds her personality from their childhood-sweet, cheerful, and well-natured-attractive. He projects this onto the Yamato Nadeshiko-esque Anthy, and Kozue, for ambiguous reasons, acts out by sleeping with numerous boys in order to spite this. Miki doesn't care for her promiscuity at all, but fails to realize that his lack of attention to her is a big reason why she acts that way. However, Kozue's need to annoy and get Miki's attention is never fully resolved either: there is sexual attraction to Miki implied, but it isn't as blatant as Nanami and Touga and, and it may also be because that she feels inferior to him, as he is a piano prodigy and a Teen Genius. Miki's A Day in the Limelight/duel episode highlights their relationship, including an incident involving their piano playing and why she stopped being sweet.
 * Please Twins! features a boy who is not sure which of the two girls in the story is his long-lost twin sister. They both fall for him, making one a case of twincest and the other not. Now, if only they knew which... If only the manga and anime were the same on that point.
 * Chobits has some extremely un-sibling-like touching between Chi and the "Dark Chi" that appears in her mind.
 * In a similar CLAMP example, see Hinoto and her hallucinatory Evil Twin in X 1999.
 * On learning that Fai of Tsubasa Reservoir Chronicle  the fangirls hit the keyboards hard.
 * The Acid Tokyo arc's Kamui and Subaru (also known as the "Vampire Twins") actually manage even more Ho Yay than their counterparts in X 1999 (where they are not related in any way). Vampirism (and new twincest possibilities) may have something to do with it.
 * Mercifully, the fanfic authors do not do this with Syaoran and Sakura and their many clones, as that would likely cause the already inscrutable relationship chart (for their fic, anyway) to actively kill those that look at it.
 * Myself Yourself has twins Shuri and Shusuke with a particularly strong relationship in the face of Parental Abandonment, with a later rumor even claiming a more illicit relationship. . The Distant Finale strongly suggests that the Subtext has become canon.
 * The Kannazuki no Miko manga ends with . This may be a variation on the Japanese myth mentioned above.
 * Let's not get started on Rociel / Roshiel's 'ambiguous' attitude towards his twin sister Alexiel in Angel Sanctuary. But then again, Rociel isn't a paragon of sanity, and brother-sister incest is one of the main themes of the manga.
 * Zero and his long-lost twin Ichiru in Vampire Knight. The 'cest is entirely irrelevant to the plot. It just needed that extra element.
 * In an example where the incest is relevant to the plot, in Saiyuki It's not known when they found out, but it was  motive for what he did after  And apparently even after they found out, they didn't actually break up or anything.
 * The Hayasaka twins from Buso Renkin, while probably not involved in actual twincest, do act a lot like a married couple, and used to recite the traditional wedding vows to each other as a game, as kids.
 * In Full Metal Panic the Second Raid, the assassins Xia Yu Fan and Xia Yu Lan are twin sisters who take showers together. And hold each other at every available opportunity.
 * The relationship between Carossa and Melissa in Gun X Sword has elements of this, though they are never so pronounced as when the two first appear and Carossa licks away Melissa's tears. Van, watching, cannot help but be a little disturbed. They are basically kids. What was there was creepy, particularly Carossa managing to imply "Abusive Relationship" while being all of twelve years old.
 * The hentai Twin Angels has a scene where a demon takes the form of one twin to rape the other. Other than that, Mai and Ai never willingly have sex, though they are forced to do so.
 * Ayashi no Ceres plays this trope quite creepily and mixes it with Rape as Drama. Also averted, in that the actual twins don't have twincesty feelings for each other; they are, however, possessed by their ancestors, who were husband and wife.
 * Suiseiseki and Souseiseki, a.k.a. the Boatlight Twins, from Rozen Maiden get this kind of treatment a lot through fan shipping. To be fair, they are an official pairing in the series itself, so it works out pretty well overall anyway.
 * By the 4th Kiss×Sis OVA, Riko and Ako convince themselves that it's not that dirty if they.
 * Though barely present in the main story of Earthian, other than a mention now and again by his assistant and close friend Raphael, Lord Michael and his twin sister Lucifel are featured prominently in an extra story, written years following the original publishing, that was included in the reprint. In the story, not only is Lucifel shown to be extra touchy-feely with Michael (not to mention possessive of him, to the point where Raphael considers her his romantic rival), it is strongly implied that  This becomes somewhat less of a shock when you consider the mangaka is Yun Kouga (see Loveless).
 * Durarara!!'s Mairu and Kururi have somewhat incestuous feelings towards one another, largely owing to the fact that they're not quite right in the head... (They don't actually consider themselves separate individuals, for starters).
 * Yosuga no Sora is the embodiment of this trope with the male lead Haruka having such relationship with his very twin sister Sora. Among the both of them, Sora was shown more crazy and obsessed with her brother as she constantly fantasizes having sex with him and gets jealous when Haruka interacts with other females.
 * Incest is the opening premise of Aki Sora, as Sora and Aki are sexually involved from the beginning.
 * D.N.Angel features some Les Yay between twins Risa and Riku, though mostly in color illustrations. There's a rather eyebrow-raisingly sensual pic of them laying side-by-side on a bed. One shall also note that they get a pinky thread of love together.
 * from Mawaru Penguindrum. sort-of:

Comic Books

 * In the Ultimate Marvel Universe, there were hints about Quicksilver and Scarlet Witch going down this road from the beginning, until
 * Marvel Comics' Fenris twins (Andrea and Andreas Von Strucker) play with this idea (and likely, each other!) fairly frequently. Shudder.
 * It gets worse.  The whole thing is portrayed just as creepily as it sounds, with even other characters around him being squicked by it.
 * Their Ultimate versions were pretty much the same, save for the bit in spoilers up there.
 * It was heavily implied in a few issues of Infinity, Inc.. that Obsidian has a crush on his long-lost twin sister Jade(this despite Obsidian being gay...). She was blissfully oblivious.
 * Top Ten's Spin-Off miniseries Smax has, although in the world they came from it wasn't the taboo issue it was in his adopted world.
 * They are clones rather than twins, but the girls in the XXXenophile story "Family Reunion" probably count.

Fan Works

 * America and Canada, the "North American Brothers" of Axis Powers Hetalia, are (assumed to be) twins and pairing with growing popularity in the fandom. It can't match the popularity of the America/England pairing yet, but it has its devotees.
 * It doesn't stop there, either. Southern Italy and Northern Italy, although not actually twins, look a lot alike, and are thus confused as twins. As a result, Itacest has a pretty loyal following.
 * Quite a few fans of Kira×Cagalli from Gundam Seed refuse to follow the canon. Mostly because of all the Ship Tease between the two before The Reveal. Also because of the innocent purepure relationship between Lacus and Kira that does not seem to get any further than hugging or Holding Hands. And the relatively frustrating relationship between Everyone × Athrun × Cagalli that pushes suspension of belief.
 * There is an Evangelion one-shot fic where a mixup occurs and another Rei is deployed while the previous one is still alive. Cue the two meeting up at their apartment and initiating some quick lesbian action... before it turns out that Rei was fantasizing the whole thing. During class, nonetheless. Overlaps with Screw Yourself, naturally.
 * From Infinite Stratos and it's obscure Fandom, there's this (un)holy fic. Rather than picking one of the member of Ichika's Unwanted Harem, the author choose Ichika's Half-Identical Twins...who's clearly hots for him. . It's Crazy Enough to Work.
 * Yoh and Hao in Shaman King are twins. In the anime, especially the 4Kids dub, Hao kept saying it was Yoh's destiny to unite with him. A lot of yaoi fangirls love Yoh/Hao. They are literally a single soul that got split in two, simultaneously explaining the "unite" Double Entendre and making this closer to Screw Yourself.
 * You mean Hao/Yoh?
 * The Hitachiin twins in Ouran High School Host Club play this up for their fangirls for the purposes of their club. They also seem to be very affectionate toward each other when the fangirls aren't watching, but this, too, could also be a game they play. Nevertheless, on one occasion where Tamaki calls them early on a weekend,
 * There are multiple examples of pairing up Netto and Rockman from Mega Man Battle Network/Mega Man NT Warrior. It's up to the Gentle Reader to decide which turns on or squicks him or her more—the game version, where this trope applies in full, or in the anime, where he's just a computer program.
 * Amiboshi and Suboshi in Fushigi Yuugi, though a lot of this is fan speculation. Especially  In an author's note in the manga, Yuu Watase claims that she didn't mean for that particular incident to seem so sexual. Suuure she didn't.
 * The revelation at the end of Chrono Crusade that are twins hasn't stopped some fans from shipping them. The fact that  really does seem to have a brother complex doesn't help dissuade them.
 * One of the fanon yaoi pairings in The Prince of Tennis involves a set of twins: the Kisarazus, namely Atsushi from Saint Rudolph (short hair, a red bandanna) and Ryou from Rokkaku (long hair, a white hat).
 * There are a few fanfics that pair up opposite gender twins Android 17 and Android 18 from Dragon Ball Z 1 2 (Both of these stories are NSFW.)
 * Many fans pair Vash and Knives from Trigun. To be fair, it is strongly implied that Knives has one heck of a brother complex towards Vash. The first big confrontation between Vash and Knives at the very end of the first Trigun manga really looks like  Which wasn't even the most disturbing thing about this scene in the first place.
 * For the fangirls and morbidly curious, it's in Trigun #2 (not Tri Max 2)
 * The Kongo brothers pairing in Eyeshield 21 fandom has a pretty good following. Agon's a huge narcissist and Unsui is very dedicated to his younger brother. It's not hard to imagine it being a little more then brotherly...
 * Twincest runs rampant in the Blue Exorcist fandom, with the Rin x Yukio pairing taking up almost 50% of all online romantic Fan Fiction (and normal boy x girl pairings less than 25%). Interestingly, there is no hint of yaoi in the actual series.
 * Ryan and Sharpay Evans from High School Musical have a suspiciously close relationship, what with singing love songs to each other and playing romantic leads opposite each other. Plus there's that video of "I Can't Take My Eyes Off of You", a song in which Troy, Gabriella, Ryan, and Sharpay all sing—Troy and Gabriella (established couple) sing to each other and Ryan and Sharpay... also sing to each other. Sample lyrics: "I can't take my eyes off of you/ I know you feel the same way too" and "You never really know what you might find/Now all I see is you and I/ You're everything I never knew that I've been looking for."
 * "If Sharpay could figure out a way to play Romeo and Juliet at the same time, her brother would be out of a job."
 * Pretty much every Boondock Saints slashfic.
 * The Weasley twins are a prime example of this trope in fanfiction. Here is a good example. It's a song called Brotherly Love by Gred and Forge.
 * After Rowling told the fans what happens to Luna, there's been a bit of twincest involving her sons Lorcan and Lysander.
 * The twin sons of Elrond, Elladan and Elrohir and (to a much smaller extent) Elrond and his twin brother Elros are frequently paired in The Lord of the Rings fanfiction.
 * Zack and Cody together have lots of fans, too.
 * Devil May freakin' Cry. It doesn't help that Dante and Vergil are ridiculously pretty and there's a lack of female characters (that don't look like their mom.)
 * Raul Gureden of Super Robot Wars Reversal would have fit the more appropriate Screw Yourself, due in fact his female counterpart Fiona Gureden are one and the same character in Reversal. However, upon getting an entry in Super Robot Wars Original Generation, the two became Half-Identical Twins; naturally, fanworks ascended it to this trope, even though Continuity says otherwise.
 * In Xenosaga, Albedo is revealed to have been the conjoined twin of . And let's just say that Albedo... was really obsessed with him, to the point where the thought of being unable to stay with him forever - among other things - drove him mad.
 * A Alternate Timeline fanfic for the Play Station 3 game In Famous, in which the twin daughters of, become twincestuous lesbians; due to the nature of the fic, also possible candidate for Foe Yay and Power of Love.
 * Lucas and Claus from Mother 3 have been treated in this way.
 * Mario and Luigi... *eeeps* *gags*
 * Gemini Man and his clones. It's one of the classic mainstays of Mega man slash.
 * Ask That Guy and The Nostalgia Critic are twins in fics most of the time, with Ask That Guy usually torturing Critic, sexually, emotionally and physically. Fun times for all.
 * A lot of My Little Pony Friendship Is Magic fan art and fan fiction involving Aloe Blossom and Lotus Blossom loves to speculate about what goes on in their spa after hours(wink wink, nudge nudge).
 * Edgar and Ellen fandom has quite a few of these.
 * If you see Sideswipe and Sunstreaker in a fanfic together, 90% of the time it's because they're banging each other.
 * Likewise, Reflector now exists purely to have three-ways. But then three identical robots becoming one camera... really is asking for it.
 * The jet twins Jetfire and Jetstorm too.
 * Kyle and Lane Carlson, twin male models. And the Brewer twins, Derek and Keith.
 * Both incarnations of Wilykat and Wilykit have gotten this.

Film
""Oh, here it is. Bratislava. Hmm. Capital of Slovakia. Oh, here's a fun fact: You made out with your sister, man!""
 * Narrowly averted (at least according to Fanon) in Star Wars: the viewers (and the characters themselves) are initially led to expect a love triangle between Luke, Leia and Han, but then it is revealed in Return of the Jedi that Luke and Leia are actually twins.
 * However, the novel Splinter of the Minds Eye was written and takes place before their relationship was revealed and so features romantic scenes with the two, as well as a scene in which Luke openly admires Leia's body. Particularly her "seal-curve hips". Apparently Splinter of the Mind's Eye was George Lucas's plan B if Star Wars wasn't a big enough hit to make The Empire Strikes Back, and would have been developed into a movie had there been no money to make the trilogy as hoped. At this point, he had not decided whether or not Luke and Leia would be family or a romantic item, but with all sources taken into context it looks like a pretty clear case of Abandon Shipping.
 * Marvel Star Wars, which also started production long before Return of the Jedi, also features a great deal of subtext early on. Notably there are many, many instances between The Empire Strikes Back and Return of the Jedi in which either Luke or Leia were trying for a Relationship Upgrade when they were interrupted by something or other. On a meta level, it was because the writers knew Han would come back and show whether "I know" meant reciprocation, but looking at it today makes it seem like the Force knew these two were twins and contrived to keep them from sleeping together.
 * The Yuuzhan Vong pantheon includes Yun-Q'aah and Yun-Txiin, sibling deities whose domain includes "love and hate and all things opposite". Their usual titles are either "The Twins" or "The Lovers". Possibly they either aren't twins or aren't lovers, and the Vong just have really confusing mythological canon. It happens. (For bonus points, a psyop plants a non-humorous meme in the Vong that the Jedi twins Jacen and Jaina are avatars of the twin gods...)
 * David Cronenberg's 1988 film Dead Ringers features some creepily sexual scenes between Jeremy Irons and Jeremy Irons as twin gynecologists Beverly and Elliot.
 * Based on the novel Twins, later re-released as Dead Ringers.
 * Definitely not to be confused with the Schwarzenegger and Devito vehicle.
 * Though that film surprisingly does have some eyebrow-raising twincest moments.
 * Creepy Twins Wendell and Darlene from the horror film The Hamiltons.
 * Pretty much the basic plot of The House of Yes, with Parker Posey.
 * Julie Taymore's film version of Titus Andronicus portrays Chiram and Demetrius this way. They're just as touchy-feely with their mom, too. It's okay, though, because Anthony Hopkins puts them in a pie.
 * Hellboy II: The Golden Army. Okay, the twincest doesn't actually happen, but boy, does Prince Badass Bishonen Faerie want it to. It could be inferred that it had happened in the past. Considering that anything felt by one is felt by both, it's likely any masturbation experienced by one would automatically be shared with the other.
 * In Eurotrip, Jenny and Jamie get trashed on absinthe and make out. They are appropriately horrified the next morning.


 * In Bernardo Bertolucci's The Dreamers, an American student befriends a Parisian brother and sister. They claim to have been been born connected at the shoulder, even though that can't happen with fraternal twins. It becomes more and more apparent that there is something very... odd about the siblings' relationship, but our American doesn't really seem to mind. Everything's fine until someone puts a brick through the window.
 * Not-so-subtly hinted at in Brothers of the Head with conjoined twin brothers.
 * Billy Zane and Gina Gershon's characters in This World Then the Fireworks.
 * Cruel Intentions 2 had a scene where identical twin sisters make out in the shower (although in dialogue they identify themselves as cousins, which is unlikely to anyone with functional eyes). This film was originally produced as the pilot episode for a Fox TV series called Manchester Prep, but the series was cancelled before broadcast and so the pilot was "spiced up" for video release. One can safely assume this scene wasn't in the TV version.
 * Stranz and Fairchild Van Waldenberg in Blades of Glory. The closeness of their relationship is a running joke throughout the movie and
 * This is also a Casting Gag as the actor and actress who play them are married in real life.
 * Very heavily implied with the twin socialite sisters ("We share everything") in Species II.
 * The Wire Twins from Hellraiser Inferno.

Literature

 * In Spencer's The Faerie Queene (1590) the giantess Aregant commits incest with her twin brother BEFORE THEY ARE BORN.
 * Cersei and Jaime Lannister in A Song of Ice and Fire. An unusual example of an incestuous relationship in serious fiction, as their affection for each other is depicted as genuine, unforced by either partner, long-term, and stable. (That affection is now rapidly waning, however.) Goes from pretty nasty to very squicky when it's revealed that they were into with each other even as little children—a servant walked in on them doing something sexual when they weren't even ten years old. Cersei even implies that the bond went back to birth, seeing as the two shared a womb and Jaime came out holding onto Cersei. This squicks the everloving fuck out of.
 * Implied in Edgar Allan Poe's Gothic horror story The Fall of the House of Usher. It was damn near outright stated, the family had a history of incest, sooo...
 * There's a rather bizarre example in Fifth Quarter by Tanya Huff. The soul of Bannon is forced to share the body of his twin sister Vree when another man steals his body. Vree goes after her brother's body, and when they find it, they devise a plan that Vree will distract him by seducing him, and Bannon will "push" the interloper out his body. Partway through, Vree realizes that Bannon is more interested in seducing himself than in getting his body back, and calls it off.
 * Twins Charles and Camilla from Donna Tartt's The Secret History are revealed to be sleeping together towards the end of the book, although it is hinted at earlier in the book.
 * Twins Estha and Rahel in Arundhati Roy's God of Small Things.
 * Shelley and Kipling in Judith Hawke's Heart of a Witch get into a very complicated relationship that was hinted at from the beginning with Shelley's possessiveness of her brother. Even more weirdly, this eventually turns into a threesome with.
 * In P.C. Hodgell's Chronicles of the Kencyrath series, Highborn Kencyr families used to practice sibling and cousin marriage extensively in order to breed Shanir (individuals manifesting powers of their triune God). Twin marriage was especially valuable for this, since it reinforced traits so strongly in offspring. Since a married pair of twins betrayed their people to the Big Bad and killed off two-thirds of them a few thousand years ago, it's fallen somewhat out of favor, but families that stick to the Old Ways still only breed with others in the extended family. It's notable that some of the results of constant incest seem to be prevalent in the Highborn; they're dying out, fertility is down, childbed mortality is high, and some families are getting rather strange indeed.
 * Children of Dune has some pretty heavy overtones about Leto II and Ghanima's relationship at times. From Leto II's own mouth: "Let us pass puberty living in the same house, and all your taboos will be as a red rag waved in the face of a Sandworm." Perhaps mercifully, he ... Of course, that doesn't stop him from marrying her later. But both of them are in complete agreement about the fact that there will be no weirdo hanky-panky going on, and that all her children will be bastards sired by a Corrino survivor, specifically the . (Though they're in love anyway, so, good for them.) Not to mention that one of the reasons Leto transformed was to avoid the certainty of being maneuvered by the Bene Gesserit into this. The Bene Gesserit themselves view this "ship" as the only way to get back control of their Kwisatz Haderach program after Jessica sabotaged it by giving birth to Paul.
 * Stalking Tender Prey by Storm Constantine has, within the first few chapters, a pair of twins who, because they are  get into twincest an awful lot. They're also Half-Identical Twins though this is not out of prudishness on the authors part, as one of them later turns out to be massively bisexual, and, lets be fair, most of the main characters do bedhop with most of the other main characters. In fact the main antagonist, as   pretty much gets to bonk 98% of the main characters. Repeatedly.
 * Incest is a common trope across all of Storm Constantine's work. Half-Identical Twins Valraven and Pharinet Palindrake are lovers in Chronicles of Magravandias. Pharinet justifies this by claiming that they are one soul in two bodies and that they are the last of a great heritage. They almost conceive a child, but Pharinet miscarries.
 * It's really, really difficult to read the opening few hundred pages of Polgara the Sorceress without reading some seriously odd romantic undertones into the relationship between (technically) non-identical twin sisters Beldaran and Polgara: not only does Beldaran have her sister completely wrapped around her adorably girly little finger, but they're apparently sharing a bed well into adolescence whenever Polgara hasn't run away to live in a tree, and Pol's explicitly possessive anger when Beldaran gets engaged would be a little freakish in its intensity even coming from an actual romantic rival. (Technically technically, they are identical, making it even more fun. The physical difference or two comes from sorcerous manipulation in the womb by the mother gearing them towards their different destinies—Polgara was going to be a sorceress and Beldaran was going to be the queen of Riva. Apparently queens should be blondes and sorceresses should be brunettes.
 * In Gene Wolfe's Book of the New Sun, twins Agia and Agilus are found to have an incestuous relationship when Severian  Agilus admits, "Everything you suspect is true," the implication being incest.
 * The Duet evil twin rulers of the Seven Kingdoms in Morgan Llewellyn and Michael Scott's Arcana series.
 * Elizabeth Lynn's The Dancers of Arun features male/male twincest between Kerris and Kel. Oddly, it's portrayed as wholly positive.
 * In Robert A. Heinlein's Time Enough for Love, protagonist Lazarus Long relates a story about a twin brother and sister he encountered who were unrelated to each other through a remarkable feat of genetic engineering, and were induced from childhood to form a sexual bond with one another for breeding purposes. As they are slaves, he buys them, frees them, and sets them on the road towards being independent human beings, but they still end up marrying each other and pumping out babies.
 * A probably nonconsensual example: in The Acts of Caine novels, in one book, Berne is revealed to keep twin sex slaves, one male and one female. This being Berne, if you think he wouldn't order them to have sex with each other, you plainly haven't read the books.
 * In Death: Rudy and Piper Hoffman from Holiday In Death are brother and sister, twins, and... have at a least a sexual relationship with one another. Rudy has admitted that they have tried not to act on the attraction between them and be with other people, but they were miserable. Miserable because they are attracted only to each other. Hoo boy.
 * A twist on this trope: The two protagonists of Alistair Reynolds' House of Suns are among thousands of both-sex clones of one woman. They are genetically programmed to be space-explorers, and all are supposed to meet once every 200,000 years to share information. Their progenitor forbid inter-clone romantic relationships and, while sexual encounters are said to occur occasionally, the protagonists' long-term consorting is strongly rebuked by their fellow "siblings."
 * Emmeline and Adeline's relationship in The Thirteenth Tale has very strong incestuous overtones.
 * Rika and Saxon Hyde from Michael Slade's Ghoul engage in this as teens. To amp up the Squick, they're the product of Brother-Sister Incest themselves.

Periodicals

 * Expect this in any pictorial featuring twins in the less classy porn magazines.
 * In 2003, Shane and Sia Barbi sued Hustler for unauthorized use of photos showing "intimate sexual acts between the twin sisters".

Live-Action TV
"Dan: How do you know so many twins? Chuck: ...Twins find me."
 * Cersei and Jamie Lannister in Game of Thrones, the television show being a faithful adaptation of A Song of Ice and Fire (see Literature above).
 * In the final episode of Arrested Development, . However, this is only after the revelation that.
 * Admits?
 * It's impossible to watch Maya and Alejandro Herrera in Heroes without thinking about it.
 * House points out that two identical female twins who are both fighting to join his team are "distracting to every man and lesbian in the room".
 * There was a pair of fraternal male twins that the main characters used to go to school with on It's Always Sunny in Philadelphia that were sexually involved. Turns out the entire McPoyle family is one large, ingrown incestual orgy. It's just about the creepiest thing on television.
 * In "Who Got Dee Pregnant," the gang (minus Dee) think that Dennis was the one who had sex with Dee at the Halloween party (due to Dennis switching costumes with Charlie and Dee with the girl Dennis was trying to hook up with). Dennis is throwing up when they confront Dee, with them telling her she has to go to Mexico to get an abortion- which she states none of them are the father and although she pulled Dennis into the back room, they didn't have sex.
 * Jack from Will and Grace has, as his life's ambition, to one day meet and have sex with a pair of male identical twins. Will once actually invited over a pair of gay identical athletic twins just to make Jack jealous.
 * Katie and Emily Fitch from Skins. Moreso Katie than Emily; she states that Emily is "hers" and Naomi (who is romantically involved with Emily) could never love Emily as much she does. It doesn't help that at one point during the end of the twins' episode in series three, when Emily is confronting Katie, someone in the crowd yells out that Emily should kiss her.
 * And in the book,
 * In an episode of Medium, some characters come across a porno that features this.
 * Definitely played with by John and Edward in X Factor, such as their routine to "Oops I Did It Again", which involved a full re-enactment the talky bit between Britney and her love interest from the music video ("but I thought the old lady threw it into the sea at the end of the movie").
 * For anyone masochistic enough to want to see them in action, here is the aforementioned performance.
 * Gossip Girl hints at this in an episode.
 * Gossip Girl hints at this in an episode.

"Tao: It says you were born in the same place... and at the same time. Gem: You are the first to understand. Tao: This has to be wrong. Nye: It's not wrong. Gem: We know our own story. Tao: But it says you were born of the same mother. (crickets)"
 * BeastMaster had a fraternal twin example in its first season.


 * Degrassi the Next Generation Twins Declan and Fiona Coyne were introduced in season 9 as being "very close."
 * In Degrassi Takes Manhattan
 * It took twelve seasons, but "SVU" finally went there in the episode "Bombshell": Elliot even calls the trope by name.

Music

 * Made explicit in Le Sexoflex's cheerfully NSFW song "Twincest". The music video features male and female twins gettin' it on with their siblings, animated by pornographic embroidery.
 * Implied when the Veronicas, a band consisting of twin sisters Lisa and Jess Origliasso, sing "All About Us", a song that, while written by them, was made famous by t.A.T.u., apparently Schoolgirl Lesbians.
 * The story goes that the song was originally a demo done by the Veronicas; when they couldn't fit it into their lineup, they handed it over to t.A.T.u. Which is not to say that the Veronicas are not twincesty as hell—see their propensity for taking ridiculously inappropriate-for-sisters pictures. Seriously. Not to mention their music videos. No...THIS video. Also this is the official video for the first link...and a little more twincest sexy
 * And at least one of them is rumoured to be a lesbian, which would presumably fuel such speculation.
 * Similarly, when Ryan Dan (another twin band, of the male variety) sing mushy romantic duets to one another.
 * Well, at least one can sing soprano very well.
 * More willfully-interpreted Ho Yay: Bill and Tom Kaulitz, of German band Tokio Hotel.(New .gif for your pleasure! More lap-bouncing, less arm-tugging)
 * So...much...fanfiction... It's staggering how...dedicated these fangirls are.
 * At least once when performing live Bill has dropped to his knees in front of Tom, while singing a song supposedly about Tom and a groupie. More specifically, he sang "Ich will mit keiner ausser Dir." Which roughly, in context, translates to "I don't want to do it with anyone but you." He ALWAYS sings that part to Tom.
 * Unfortunately, though, "keiner" denotes a female "anybody" (the male form would be "keinem"). Which either rules out the homosexual context or says things about Tom we'd better not go into.
 * That line has also been translated as "I won't do anything without you" as in "without your conset, i.e. not going to rape you" which makes more sense as "Reden" is about a one-night stand. Not sure what effect that has on the implications.
 * Bill has also commented on these stories saying: "Everybody can have his fantasies... though they are sometimes really absurd... but they do exist for that..." Hmm-HMMM.
 * "I'm ready to fall, I'm ready to crawl right on my knees to know it all." Practically on his knees in front of Tom while admitting he's okay with being down there? Oh Bill, learn some subtlety.
 * This seems to be the gist of the relationship between the Kagamine twins of Vocaloid, at least among the fandom. Though they look like twins, Crypton originally presented them as such before making them "mirror images," then finally telling the fans to decide for themselves.

Oral Tradition, Folklore, Myths and Legends

 * In the Feri Tradition (one of the Neo-Pagan movements), there is a pair of twin gods who basically share all aspects of themselves with each other (and not just in that way), or so claims The Other Wiki. They also don't have a fixed gender.
 * Norse Mythology: In "Lokasenna" of the Poetic Edda, Lok accuses Freyr and Freyja, the sibling fertility deities, of sleeping together, though it's unclear whether this is 'truth' or not.
 * In the Volsunga Saga, Sigmund is seduced by his sister Signy in disguise, as she believes only in this way she can conceive a son that is strong and loyal enough to help Sigmund avenge their brothers and father on their killer, Signy's treacherous husband Siggeir.
 * Egyptian Mythology had Osiris and Isis, as well as Set and Nephthys, the four of which were all twins who fell in love while still in the womb together.
 * The Sioux say twins are the reincarnation of lovers. Whether Everyone Is Bi or Unto Us a Son and Daughter Are Born is another issue.
 * The story of Byblis and Kaunos in Ovid's Metamorphoses.

Theatre

 * This trope (along with a helping of Creepy Twins) is the premise of Marina Carr's play Portia Coughlan. Portia is haunted by her twin brother Gabriel, who drowned himself as a teenager; the fact that she's still obsessed with him fifteen years later (and that Gabriel is referred to as "unnatural") hints heavily towards this, so it's no surprise when she reveals that their relationship was sexual. It's a bit more surprising when
 * Bat Boy: The Musical: ... and it's an Interspecies Romance too!
 * ... How can you have a twin who's not the same species as you?
 * The entire plot of the rather strange—and very sexual—British queer play Over There. The two-man cast consists of the identical twins Harry and Luke Treadaway, and I can only say that the two certainly aren't uncomfortable with each other.
 * Part 2 of Richard Wagner's operatic The Ring of the Nibelung cycle, The Valkyrie, has Siegmund and Sieglinde: Twins separated at birth, who meet as adults and fall in love which each other, finally giving birth to the legendary hero Siegfried.

Video Games

 * Resident Evil: Code Veronica implies that Alfred's devotion to Alexia goes some way beyond mere intense admiration.
 * The novelization pretty much states it outright.
 * Visual novel Yosuga no Sora most famous pairing Haruka and Sora are twins and the fact that Sora is even implied to masturbates by imagining having sex with her brother BEFORE the game even started clearly doesn't help...
 * Metal Gear Solid, being chock full of Ho Yay moments, certainly didn't shy from playing with this trope. In the first game, Liquid Snake strips Solid Snake's shirt off while the latter was unconscious, and there was his desperate need to prove that he was the dominant brother. Naturally, it's kicked up to overdrive in the remake. It also certainly didn't help that Liquid was a Large Ham and his voice actor, Cam Clarke, seemed to have an uncanny ability to make the word "brother" sound very erotically incestuous.
 * Liquid does blatantly say that part of his motivation is that, 'in Nature, family members don't mate with each other, but they help each other to survive'. Bad biology aside, it's pretty easy to overthink how that would justify him killing his brother instead of 'helping him to survive'
 * Fatal Frame II: Crimson Butterfly, with their whole "becoming one with your other twin". One of the key plot elements of the game is the fact that and then they'd get to be togeetheeer foreeveeer. This whole "I want to be with only YOU, -insert other twin's name here-!!" thing happens with prettymuch all of the Twin Shrine Maidens depicted in the game, including but not restricted to Azumi and Akane Kiryu, the protagonist Mio and her sister Mayu, and the antagonist Sae with her sister Yae. Sae seems to be the one with the most weirded-out obssession with her sister, since  by the end of the game you find a crystal left by her that is pretty much along the lines of
 * Not to mention in the promotional comercials, Mio and Mayu are shown in a number of amusingly suggestive poses together.
 * Aaaaand some official art has them sitting together or swiming together in bikinis. Very... very closely.
 * In the PSX RPG Dragon Valor, the grandson and granddaughter of Clovis, the game's first protagonist, are fraternal twins who are the "most important thing" to each other. It is revealed in the final scene that they are forced to keep their love a secret most of the time as they can only freely express their mutual affection in places where "nobody knows that they're the prince and princess" (i.e. brother and sister).
 * In King's Quest III, after Alexander frees his twin sister Rosella and talks to her, he seems attracted to her in a not-so-platonic way. Of course, they were also Separated at Birth.
 * The same reason was why a lot of Phoenix Online players were scratching their heads at the opening scene of The Silver Lining (a Fan Sequel to the series). Sure, it makes logistical sense to keep the comatose twins in the same room where their respective spouses can act as a final line of defense...but the same bed?! Um...NoYay.
 * In Odin Sphere,
 * Weiss and Nero from Final Fantasy VII: Dirge of Cerberus. Oh. God.
 * God is an understatement for this cause
 * In the second Rune Factory game as your child you can "marry" a set of twins, even if you're a girl. They're blissfully naive though so they most likely didn't think too much into it.
 * Amber and Crystal Bailey in Dead Rising 2. Then again, they both hit on Anything That Moves.
 * Lucjan and Myaja, a brother-and-sister fighting team in Dragon Age, state that "everything they do, they do together." When the PC asks them if that means everything, Myaja asks if he wants to find out.
 * Duke Nukem Forever has the "Holsom Twins".
 * In The Sims 2, if you turn off the switch that prevents incest relationships, twins fall in love very easily, without intervention from the player. Mechanics-wise, it is probably due to their interests and personality traits being alike, therefore making the "perfect" match as far as the game is concerned.

Web Comics

 * Fraternal twins Lucy and Fisk in Better Days. Whether it happened more than once is a matter of debate. Lucy at least continues to have more than sisterly feelings for her brother well into college.
 * Given that there are several early Naylor porn-folios centered around Lucy and Fisk, it seems likely that they were at least originally intended to have a long-running relationship... then again, those portfolios are stricken from the record as far as Naylor is considered, mostly because the copyright notices affirm that Lucy is not his original creation.
 * Rick and Kate in Concession, though that is not by any means the only way they are messed up. Also.
 * The twin lawyers in Devil Bear have a strong vibe of this going. Given that they are infernal servants and borderline Horny Devils, it's not unexpected.
 * Subverted in Oglaf. While trapped in his Lotus Eater Machine, Ivan's love interest says she's delivered twins and shows him... two minature copies of herself making out. Rather than be a turn on, it's the sight that makes Ivan briefly realize it's All A Dream.
 * Succubus twins Giselle and Alizee in Leth Hate, although not voluntary on Giselle's part.

Web Original

 * Whilst nothing explicit has happened (Yet?), Survival of the Fittest V3 characters Lenny and Elizabeth have a whole lot of Subtext in their relationship, prompting a lot of "speculation" amongst members of the board. It isn't clear precisely what relationship the pair have, but it is implied it goes further than being simply siblings. Recently the handler more-or-less addressed this issue, quoting a Fanfic in this first half of one of his posts.
 * In Tea, Biscuits and Incest,
 * A vast thread on the RPGNet forums, covering creepy gamers, had a poster effectively troll the discussion by promising to elucidate on a story of creepy gamers that involved twincest. Although there were several Crowning Moments of Awesome and Funny involved on the thread as it was, the rumoured story turned out to be disappointing, though it did get an airing.
 * A lot of fanart depicts Hacchan and Secchan, the Moe Anthropomorphisms of Windows 98 First Edition and Second Edition respectively, together. This one's safe for work, but most others aren't. And even those that don't depict the 98 twins being mutually attracted to each other often have Secchan acting Yandere for Hacchan.

Western Animation

 * Robot Chicken
 * The show has a long running gag portraying the Bush twins, Barb and Jenna, as hard-partying Girls Gone Wild types, often ending with the two of them making out.
 * During the Star Wars special, there was the inevitable skit involving Luke and Leia in bed.
 * Invoked in Young Justice. Superboy and Miss Martian go undercover as two twins. While in their disguise they make out, and it takes a while for the latter to transform back into her normal self. Much to the horror of Icicle Jr.