Basically this is when Father, I Want to Marry My Brother goes horribly wrong. For some reason a person really does want to marry their sibling. Even though they understand what that means. This is most commonly depicted in the form of a younger sister who has developed some sort complex or obsessive attraction to her older brother. Perhaps because he protects her. Or maybe because he's the only man in her life that she feels safe with.
Sometimes it's suggested that it's not so much that she wants him. Rather that she doesn't want to lose her brother to all those other girls who are stealing him away from her- so she decides she'll provide her brother with whatever it is he seems to want from other girls. This is still rather squicky, but might be a little closer to the innocence of Father, I Want to Marry My Brother. Sometimes might be part of a Token Loli.
May or may not be a factor with a Younger Sibling Fetishization.
Anime and Manga
- Belarus from Axis Powers Hetalia takes this to hilariously dangerous levels. She wants to marry her brother, Russia. She's also Russia's Ax Crazy Stalker with a Crush, going so far as to hunt him down with knives and break down a door when he barricades himself in an attempt to hide from her. South Korea has a similar if less violent complex with his older brothers China and Japan, especially the former, constantly attempting to grope them; they see him as the Annoying Younger Sibling and want nothing to do with him, while he refuses to accept that they don't like him.
- In Magikano, Maika has a huge complex regarding her big brother Haruo. She's always showering him with affection, hiding in his closet and watching him sleep, trying to bathe him, modelling lingerie for him to see (even wearing it on top of her school uniform to give him a little preview), and attempting to drive away any and all other female attention from him.
- Yoh Takami in Deadman Wonderland is called a "sister-complex freak!" by his sister Minatsuki. Given that they're in prison and DW is a Seinen series, this could be either Pet the Dog or Squick or both, considering what how sadistic his sister is.
- Many characters in Tenjho Tenge remark on Maya's Big Brother Attraction regarding Shin. It's almost to the point of Brother-Sister Incest.
- In Revolutionary Girl Utena, Nanami lets everybody know that her big brother Touga is the best. She is so obsessed with being onii-sama's sole target of attention that she got rid of his kitten and humiliates a girl from her Girl Posse. After realizing what a Manipulative Bastard her brother is, we see how her hopeless devotion to him is actually quite tragic.
- Oniichan Control. The little sister openly admits to people she barely knows how in love she is with her big brother. Played for some combination of horror and laughter at how over-the-top it all is.
- The Yandere no Onna no Ko Drama CD series is based on this + Axe Crazy. The listener is in the position of "onii-chan" (the big brother), and gets to listen as the various little sisters explain in detail just how crazy they are.
- Might be the case with Kotomi in Seitokai Yakuindomo. She likes invoking Brother-Sister Incest (especially in the Yonkoma), Episode 12 has her admitting that she had an incestuous dream, and she also mentions that she and her brother Tsuda sometimes get mistaken for a couple, which she plays up. When her friend notes that it's sometimes hard to believe the two are related because of their very different personalities, Kotomi gets excited and interprets the comment as a possibility that they might be Not Blood Siblings.
- Kotomi also has no problem taking her clothes off in front of her brother and once proudly mentioned to the other girls that he's also "impressive down there," which has him wondering as to when the hell she managed to sneak a peek.
- Imouto wa Shishunki (My Little Sister is Going Through Puberty), made by the same mangaka as Seitokai Yakuindomo, has a little sister who makes extremely perverted statements around her big brother and has constantly hinted in a blatant manner that she wants to do more than sisterly things with him.
- Akiha from Tsukihime is attracted to her older brother, though she usually hides it under antagonistic behavior. Though they're Not Blood Siblings.
- Notably, she's the only heroine with endings and no "Good End". Either Shiki dies (the True End), or she becomes a vegetable (the Normal End). Nasu is definitely against Brother-Sister Incest.
- Also from the Nasuverse is Azaka of Kara no Kyoukai, which is fitting given that Akiha is something of an Expy of her. Azaka is in love with her brother Mikiya, and left to live with their uncle and attended a different school in the hopes that he would think of her as something other than a little sister.
- Nadeko Sengoku from Bakemonogatari is this towards the male lead, calling him Koyomi-onii-chan.
- Although this is probably more due to Japanese language than a true big brother complex. Young girls often call slightly older boys "oniichan", especially if they are somewhat close or friendly with each other.
- Although Haru and Sora from Yosuga no Sora are actually the same age, they are commonly referred to as 'older brother' and 'younger sister', and Sora otherwise exhibits this trait very well. Haru is a bit more receptive than most examples here, though.
- In Witch Craft Works, Takamiya's sister has a blatant crush on him, but she's in denial, claiming her actions are just her right as a little sister. Hilarity Ensues.
- Code Geass has its own page on the incestuous subtext between siblings, with Nunnally and Lelouch being the most obvious example.
- Jackie from The House of Yes goes beyond finding her brother attractive. The two of them actually had an affair in the past.
- Done in the Darkover series with Stormqueen! Everyone's already disturbed by the father suggesting he marry off his daughter to her half-brother, but then Dorilys starts to get into the idea, and Donal gets used to it...
- In The Borgias, Lucrezia and Cesare seem a little too close, with her saying that she will never love her husband as much as she loves him. Cesare seems to reciprocate, saying that if her husband proves "ungallant", "I will cut out his heart with a dinner knife, and serve it to you", in a very low, breathy whisper, while nearly giving her a Headbutt of Love, and this is just after he has carried her up to her bed on her wedding day. Given the historical characters they're based on, though, it would be surprising if there wasn't a lot of incestuous implications in the show.
- The song "Ark" by Sound Horizon implies this by naming the two characters involved "Frater" and "Soror". It ends badly. Or does it?
Oral Tradition, Folklore, Myths and Legends
- In The Bible, Dinah either has an affair with, or is raped by, a man called Prince Shechem, who then agrees to marry her. However, two of Dinah's brothers, Simeon and Levi, instead go to war against Shechem and kill him. In one Jewish legend Dinah, angry and fearing that she was Defiled Forever without her fiancé, demands that Simeon marry her. He formally does but never sleeps with her. (This is the interpretation of a later verse, when it mentions "Saul, the son of the Canaanite woman" [Dinah] being a member of his household.)
- In one Arthurian legend a princess falls in love with her brother. A demon offers to make the prince love her back, as long as the princess and demon sleep together. Instead the princess gets pregnant and the demon turns her love for her brother into hatred, so that she accuses him of raping her. He is executed, but first declares his innocence and predicts that his sister will give birth to a monster. Indeed, her child winds up being the Questing Beast.
- Albedo from Xenosaga has a huge Big Brother Attraction with his twin, Junior. He becomes something of a Stalker with a Crush towards him, and was shown to have gone crazy due to the revelation that he wouldn't be able to stay together with him forever.
- Sayu in the original Death Note Abridged by TioH and Dargonakis. Who isn't particularly subtle about it.
- On Phineas and Ferb, this is one interpretation of Susie to her older brother Jeremy. If nothing else she seems to fit the "doesn't want to lose him" model, as she's fiercely jealous of Candace becoming his new "favorite girl."