Matchmaker Crush

""Oh, get over it! You can admit it, can't you?! I mean, she is beautiful, and she is kind... How could anyone not have feelings for her? (...) But I guess I will have to let you take the lead here, since that is truly the knightly thing to do for one's partner...""

- Sain towards Kent, Fire Emblem Elibe

A character starts out trying to help one character hook up with another, but ends up in love with the person they were helping (or worse, the person they're trying to help them get), seriously undermining their own efforts.

Why? Perhaps they felt unworthy and just wanted their beloved to be happy, but in the end just can't resist their own feelings. Or maybe their intentions were pure at the beginning, but the excessive attempts to help their target caused feelings to bloom.

Wife Husbandry can be mitigiated if the older man heroically tries to pair the younger woman off with men her own age.

Love Triangle-arity ensues. An easy way to obtain a Downer Ending. See also Playing Cyrano, another intermediary type who generally isn't in love with the target.

Anime and Manga

 * Shakugan no Shana: Hayato Ike often helps Kazumi Yoshida to hook up and show her affection toward Yuji. When he chastises Yuji for leading her on, Yuji confronts Ike about his own feelings for her. It took him until the second season for Hayato to realize it and tries to do anything for himself, for the sake of his feeling toward Kazumi.
 * School Days: Sekai helps Makoto and Kotonoha hook up and puts a lot more effort into it than you would expect. Then she gives herself a reward for her efforts by surprise-kissing Makoto. This does not end well.
 * There's actually a recursive variant, as Sekai is in turn assisted by her best friend  Setsuna who also has a crush on Makoto.
 * Kashimashi: Girl Meets Girl: Tomari pushes Hazumu to confess to Yasuna, ends up dragged into the Yuri Love Triangle that is the main plot
 * Clannad: Throughout the Anime series, at every opportunity Kyou tries to push Tomoya to be with her twin sister Ryou, even though she too has a crush on him. And in the Visual Novel, Ryou doesn't even get a real route. Well, she does, but it doesn't count towards the true ending of the story.
 * Video Girl Ai: Ai falls for Youta, the Unlucky Everydude she's trying to hook up with his female friend Moemi. He, ironically, was trying to hook up said friend with his best friend, Takashi. (And his selfless act is what lets him get Ai's help in the first place...)
 * Lovely Complex begins with Huge Schoolgirl Risa and The Napoleon Otani trying to be mutual matchmakers for each other. They fail (their respective partners fall for each other and become the Beta Couple), only succeeding to underline to everyone else just how much better they'd do as a couple themselves.
 * Ryuji and Taiga of Toradora! are another example of mutual matchmakers falling for each other.
 * Yue Ayase in Negima acts like this for Nodoka. First, she has no interest in Negi. Then she starts becoming attracted, but suppresses it. Eventually, Yue gets found out, and decides (and is encouraged) not to fight it anymore. They still stay friends, and Nodoka comes up with an interesting solution that embarasses her.
 * Haruna aka Paru plays with this, she's acting as matchmaker for both Yue and Nodoka. After Negi's battle in the Ostian tournament she declares she has fallen for him... then laughs, declares she was kidding, and gets yelled at for her joke.
 * And now we have, who asked Negi directly to go the Pactio route with   but refused to get one for herself.   Lampshaded by Chamo right before the last fact happens.
 * Hayate the Combat Butler: Sakuya gave up her own spot in a high-class school so that her childhood friend Wataru could go to the same school as another childhood friend, Isumi, he has a crush on. She also loudly complains about his lack of progress in confessing his feelings to Isumi. A lot of the Ship Tease in the later chapters, however, suggest very strongly that Sakuya has a crush on Wataru herself.
 * There's also Hinagiku vowing to help Nishizawa but liking Hayate herself. Isumi has something similar going with Nagi, but unlike Hinagiku makes no attempts on her own behalf as well.
 * Of course, Nishizawa would gladly share Hayate with Hinagiku...or is that share Hinagiku with Hayate?
 * Akane in Suika eventually regrets that she set up Touko and Yoshikazu.
 * In Kaichou wa Maid-sama, ships Usui/Misaki, but recently realizes he likes Misaki too. Despite this, he is genuinely happy for Misaki's relationship with Usui because being with him makes her look "cuter," and  likes it when Misaki looks cute.
 * In Kannazuki no Miko actively pushes  to date Souma because she wants her to be happy.
 * In Rumbling Hearts, Haruka enlists the help of her friend Mitsuki to hook her up with her crush Takayuki - only for Mitsuki to develop feelings for Takayuki herself. (It's somewhat ambiguous whether she already had feelings for Takayuki before Haruka asked her to set them up.)

Film

 * A brief subplot in When Harry Met Sally... finds Harry and Sally setting each other up with each other's best same-gender friends. Unfortunately, said friends hit it off immediately with each other, leaving Harry and Sally to continue to deal with their own feelings.
 * French Kiss: Luc starts out trying to help Kate win back her ex-fiance Charlie, but falls for her in the process. Somewhat subverted in that he doesn't realize this until after the plan succeeds.
 * In American Pie 2, Michelle helps Jim get Nadia, the girl he's always been in love with, only to find that she's fallen in love with him.
 * He's Just Not That Into You sort of has this. Jason Long's character doesn't realize he loves Gigi, the girl he was teaching about men and dating, until after he turns down her advances (she had a crush on him, mistaking his kindness for interest. Subconscious attraction?).
 * The Ugly Truth: The lead characters start to get along when he helps her get together with the guy she likes. Of course, then the two start falling for each other...

Literature

 * Emma shows the one way to make this scenario more awkward: Emma tries to hook up Mr. Elton with her best friend Harriet. The result is Mr. Elton falling for Emma!
 * In a similar Jane Austen example, Edmund Bertram of Mansfield Park spends some time shipping his future wife Fanny Price with Henry Crawford.
 * Only In The Movies combines this with Playing Cyrano. Vanni, a bright but unnatracive girl plays Cyrano for her close friend Jake, despite having a huge crush on him. Don't worry: he figures it out eventually.
 * In an L. M. Montgomery story "The Education of Betty", a man, having been the best man while his best friend marries his true love, then did his best for the widow and orphan. When the girl is grown up, he tries to pair her with a man his own age, and demands to know why she refused—whereupon she declares her love. Prior to that, his awareness had been limited to realizing that her mother was not so perfect after all, lacking her daughter's spirit.

Live-Action TV

 * Inverted in Frasier. Hollywood Dateless Frasier hires matchmaker Charlotte to find him a woman, and after a truly classic Terrible Interviewees Montage, ends up falling for Charlotte instead.
 * Skins does this in the S4 finale;
 * In Charmed, Coop, a cupid who's job it is to find true love for people, falls in love with his charge, Phoebe.
 * In Gossip Girl, Chuck spends the first half of Season 1 trying to help his friend Nate have sex with Blair. And then the second half trying to prevent them having sex.
 * On Home and Away, Rachel has twice set her coworker Julie up with her male friends, only to discover that said friends were more interested in her. This was previously done to Rachel, when Dan and Leah tried to set her up with Peter only to discover that Peter was in love with Leah.

Manhwa

 * The Korean manhwa Green Boy has a more direct spin on this. Ha-Eun has a crush on Taejin, who is already on crushing on Jae-in. Since Ha-Eun wants to be friends with both Jae-in and Taejin, she happily pushes them both toward each other even as she makes no secret about her crush on Taejin to both of them while assuring them that she'd never act on it because she finds them both adorable together. The trope is played with, however, when later chapters show that this is partly a facade, and she visibly struggles to stifle her Green-Eyed Monster the first time she sees them kiss.

Newspaper Comics

 * Peanuts:
 * Marcie trying to set up Charlie Brown and Peppermint Patty, while liking Charlie Brown herself.
 * Linus trying to set up Charlie Brown and the Little Red-Haired Girl, but turning out to like her himself (unfortunately for Charlie, Linus is way smoother than he is).

Theatre

 * The original Cyrano De Bergerac—that is, the original play, not the real person he's very loosely based on—provides a retrospective Matchmaker Crush. Cyrano has been in love with his cousin Roxane for years before she and Romantic False Lead Christian (who happens to be a friend of Cyrano) first meet, and Cyrano helps hook them up because I Want My Beloved to Be Happy, not because he likes the False Lead.
 * Viola in Twelfth Night ends up Playing Cyrano when she's disguised as a boy and the man she's fallen in love with sends her to the girl he likes with love messages. Then the girl falls in love with her....
 * Julia in Two Gentlemen of Verona, worried about her love interest who's been away, disguises herself as a boy and follows him. To her dismay, she finds him running after a different girl, and when he doesn't recognize her in her disguise she ends up delivering a love note for him.
 * Launcelot in The Merchant of Venice is the go-between for Lorenzo and Jessica, delivering their love messages and generally helping them with their elopement. However, he's fond enough of Jessica that many productions interpret their relationship this way. Lorenzo himself can't help but wonder, at one point joking that he'll get jealous if Launcelot keeps stealing Jessica for alone time.

Video Games

 * Quoted above: Sain from Fire Emblem Rekka no Ken tells such phrases to his best friend and partner Kent in their B support, having noticed Kent's Bodyguard Crush on their common lady of liege Lyndis, whom he also has a crush on. (Then again, this is Sain we're talking about.)
 * Subverted slightly in that Sain and Lyn can't actually support. Possibly because, in-story, Sain would rather avert being alone with Lyndis than have his feelings for her "betraying" him.
 * In Tokimeki Memorial, your best friend (alias, the main guy's friend) Yoshio Saotome is always ready to help out with tips about the girls in the game. However, he might have feelings for one of these ladies as well... Lucky for you, he's more likely to fall for your girl's friend (i.e.: if you woo Shiori, he may hook up with her best friend Megumi) than fight you.
 * Tokimeki Memorial 2 has Kotoko Minaduki, who wishes for her best friend, Hikari (the heroine, and main love interest of the protagonist) to finish with her childhood friend of a protagonist. Being a solid Type A Tsundere, she will NOT hesitate giving Armor Piercing Slaps to him if she ever feels he neglects Hikari. Yet the protagonist can woo Kotoko (much to her resistance to her growing feelings for him), leading to this trope, and {spoiler|a Slap Slap Kiss (coming all from Kotoko) Crowning Moment of Heartwarming on Kotoko's ending where she and Hikari are in love with the protagonist}}.
 * Tokimeki Memorial 4 has Miyako Okura, a Hidden in Plain Sight Secret Character who's more than happy to play the part of The Matchmaker, in spite of being an Unlucky Childhood Friend... Unless you manage to nag her into a date.
 * In Tokimeki Memorial Girl's Side 2nd Kiss you can get an ending with Yuu, the kid that gives you all the info about the possible romantic interest of the game and that has a very obvious crush on you.

Visual Novels

 * In Rumbling Hearts, Mitsuki does her best to hook Takayuki up with Haruka, only to end up paired with him after the accident. Granted, she had a secret crush on him before that but it only fully blossoms after Takayuki and Haruka start going out with her help.
 * Rider in Fate/stay night, judging by Hollow Ataraxia. She's clearly pushing Sakura and Shirou together the best she can (very awkward, uncomfortable and dangerous-feeling way) in Heaven's Feel, but in the sequel she's revealed to have something of an attraction to him as well. Oh, and Sakura gets very jealous when Shirou admits that Rider is very beautiful and he likes her. He means it in a completely platonic way, but Sakura's self esteem isn't very good.
 * Interestingly enough, being nice to Rider still gets you Sakura points—and this includes the scene where Shirou says Rider is pretty. OT3?
 * In Katawa Shoujo, we have
 * This may have happened in 's path too.

Web Comics

 * Inverted with Candi. Linda tries to convince Candi to leave her boyfriend, and winds up falling for him during her scheme to break them up to help Candi.
 * Variation in Homestuck - Jane has a crush on Jake, but when he asks her if she feels that way for him,
 * Dangerously Chloe starts with Teddy accidentally contracting a succubus. But that being Chloe, she would just as well not kill him, drag him to Hell and make his little sister cry. So she finds a loophole: if Teddy can get a girlfriend on his own, the contract is void. With which she may even "help". This turns out to be not as easy as it sounds… for either of them… and it doesn't help that meanwhile she lives in his house.

Western Animation

 * Linus seems prone to these in the Peanuts specials. In Someday You'll Find Her, Charlie Brown, he ends up falling in Love At First Sight with Charlie Brown's "dream girl", completely forgetting that he spent the entire special trying to track her down so that he could introduce her to his friend.
 * It really, really didn't help that the "dream girl" actually... very similar to Linus. She even had her own Security Blanket!