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 of 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 Mini-Moe. If it's the elder brother who develops the attraction to the younger sister, you're looking at Little Sister Heroine, although both can occur simultaneously.
No relation to Big Brother Is Watching.
- 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.
- Even worse with Ganta and Shiro — they're stepsiblings, and Shiro loves Ganta even though she's just a sacrifice so that he can live. Ganta himself was conceived as a 'homunculus' by his mother, but she warmed up to him and adopted an albino instead (implied to have been abandoned at birth for obvious reasons). The resulting rape of all things good in her (by her father-figure) leads to her Suicidal Cosmic Temper Tantrum. Also, her ultimate goal is to get married to death by Ganta's blood bullets.
- 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.
- Many characters in Tenjho Tenge remark on Maya's Big Brother Attraction regarding Shin. It's almost to the point of BrotherSister Incest.
- In Revolutionary Girl Utena, Nanami lets everybody know that her big brother Touga is the best. She is so obsessed with being her 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. It's implied that Nanami does have some sexual feelings for Touga, as shown after she watches him shower, but after she sees a real case of BrotherSister Incest, she's traumatized by it and is no longer as fixated on Touga after that.
- 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.
- In the Yandere No Onna No Ko Drama CD series, Nagisa is the listener/protagonist's younger sister. In the second CD, Yumemi is the protagonist's cousin, but she calls him onii-chan. Nana and Nono also call him onii-chan, but they aren't related to him.
- Might be the case with Kotomi in Seitokai Yakuindomo. She likes invoking BrotherSister 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.
- 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 it's own page on the incestuous subtext between siblings, with Nunnally and Lelouch being the most obvious example.
- Urusei Yatsura: Asuka Mizunokuji, younger sister of baseball-nut Tobimaro and his rival Mendo's fiancee, was raised in isolation due to family tradition and as a result she's terrified of the mysterious, monstrous man-folk (not that she should be, she's one of the strongest human characters in the series). Because she was told that "big brothers are the best kind of men", Asuka fell in love with Tobimaro, who is squicked out of his mind but can't do a lot about it because Asuka is genuinely (if hilariously) screwed-up due to how specially she was raised. She eventually does fall for Mendo after it's explained that he's a big brother too.
- Freezing: She calls him "Onii-sama" but Ouka Tenjouin is actually Kazuya's cousin and she's gonna marry him no matter what. In an unusually assertive move the Nice Guy Kazuya tells her to her face, in front of her team and his love interest (and her rival) Satellizer, that he doesn't love her like that, he doesn't want to be their grandfather's "toys", and he wants her to be happy. The girl's response is that she does love him, he will make her happy, and most importantly their grandfather's word is law.
- Girls Bravo: One of the later episodes had Kosame chase Kiriei around the house, while calling her "big sister". Which Kiriei points out as being ridiculous, since they aren't related and because Kosame is older than she isnote . But she relents after Kosame corners her at the top of the stairs and tackles her so Kiriei was sitting with her back pressed against the wall, while Kosame happily nuzzled her cheek against her breasts.
Kiriei: (mumbling, with wry grin) "Fine, you win. I'm your damn "big sister."
- The OAV adaptation of the hentai game Ko-ko-ro... features quite the literal example, as Asuka Kuonji treats her brother, Souji, as if he were her boyfriend instead of her brother. When they are out in public together, she is affectionate and clingy with him, which, of course, is shocking to everyone around town (who apparently know that they are siblings). Souji and Asuka have sex regularly, until he begins having a relationship with his teacher, Mizuki. Asuka, of course, is not happy with this development.
- In Oreimo, Kirino always wanted to marry her brother since she was a little girl. They eventually start dating and hold a fake wedding. They do break up and say they will be normal siblings though it is implied that they are still secretly together at the end of the novel.
- Hybrid X Heart Magias Academy Ataraxia: Of all the Hybrid Gears in Kizuna's harem, the one he's most attracted to is his 27-year old sister, Reiri. The narration of the volume 13 epilogue chapter explains that she's the one he most often has sex with and that it's only during those times that he feels he can be completely honest about his body's desires.
- Jewelpet (2009): Diana has a pretty obvious, but not too explicit, crush on her brother Dian. She fangirls extensively over him and wistfully fantasizes about living like a married couple. Dian never responds to this.
- Lady Jewelpet: Lillian has feelings for Cayenne, which turns disturbing when it's revealed he's her brother. Granted, later it turns out they're not siblings and their memories of each other are false. Through Character Development, Lillian does grow out of these feelings and turns her attention to Miura.
- Jewelpet: Magical Change: Played with; Laura holds obvious romantic feelings for Sakutaro, Airi's brother. The twist is that Laura wants Sakutaro to be her big brother, instead of Airi's.
- Queen's Blade makes it explicit that Elina lusts after both of her older sisters:
- The very first episode has her bemoaning the fact that she wasn't allowed to sleep with Leina. But the feeling isn't mutual, which is part of the reason Leina ran away from home and doesn't intend to return. Though she indulges Elina on occasion, such as the ninth episode of the second season, where they're shown spooning in bed while both were in the nude.
- In the "Hide & Seek" continuity, it's shown that she secretly has feelings for Claudette as well. There's even a romantic subplot that explores their hidden feelings for each other, which has Claudette believing that her love for Elina is unrequited. It isn't until chapter 28 that she becomes aware that Elina wants her too.
- Bubblegum Crisis: In the OVA continuity, Mackie pervs on his big sister, Sylia, every chance he gets, which she actively tries to discourage. The first episode shows her reading the morning paper in her nightgown and a robe. When she noticed his grin, she followed his line of sight and saw he was staring at her cleavage; causing her to whap him with the paper, before getting up to get dressed. While a later episode had him admit being disappointed that he'd been late bringing her the paper, since he had missed his chance to see her in her underwear again.
- Shoujo Sect: Innocent Lovers: The first episode focuses on Chizuru's hidden feelings for her older sister, Shigure. Though she neglected to mention that when she went to Naitou for advice, who told her to just say so and get it over with. Adding that she didn't want to hear anymore about it until she'd done it and wanted proof. Chizuru confessed her feelings to Shigure that night and learned that the feeling was mutual. The next day at school, Chizuru keeps her word by showing Naitou a photo of them in bed together, which she had taken with her cellphone camera. When Naitou finally saw who the other girl was, she regretted having said anything since, had she known, she would have advised against it.
- I Can't Understand What My Husband Is Saying has Hajime's younger brother, Mayotama. For extra levels of creepy, he also draws them as the subject of his Yaoi.
- In Sword Art Online, the protagonist's sister Suguha wrestles with complicated feelings for her brother which seem to include romantic love. This is somewhat mitigated by the fact that, although they were raised as brother and sister, Kazuto is actually her first cousin who was adopted by his aunt and uncle (they learned this when Kazuto was ten). To further complicate matters Suguha then begins to fall for Kirito, Kazuto's avatar in the MMORPG Alfheim.
- Genesis of Aquarion: Silvia is very obviously attracted to her elder brother Sirius, won't tolerate an unkind word against him, and is quick to sing his praises. This seems to generally be because Sirius is thought to possibly be the Reincarnation of Apollonius, who was the lover of Celiane, whom Silvia is a reincarnation of. When Apollo is discovered and is found to be a very strong candidate for Apollonius's reincarnation, she absolutely refuses to believe it. It's eventually revealed that both Sirius and Silvia are reincarnations of Celiane. The attraction Silvia felt wasn't romantic love, it was the unconscious desire of her soul to reunite with its other half.
- Inverted in Yuru-Yuri with Akane Akaza, who has an unhealthy obsession with her younger sister Akari, to the point of stealing her panties and having a custom made body pillow with her likeness.
- Defied in Kaguya-sama: Love Is War, where Kei deliberately avoids any action that could be construed as her having a brother complex. This results in her acting like a (platonic) Tsundere towards him.
- Yandere Heaven tends to provide a character with incestuous feelings for the protagonist. This has been played both straight and inverted depending on the character provided. The original series, which involves a female protagonist, had a few younger brothers (Kakeru, Yamashina, and Ayumu) as well as older brothers (Naohiro and Kasumi). They all harbor feelings for the protagonist, despite their blood ties to her. When another guy expresses an interest in her, he gradually becomes more obsessed with her and violently jealous of the guy to the point where he considers murdering him.
- Two of the girls in Yandere No Onna No Ko love their onii-chan enough to want to marry him as well as kill any girls who try to take him away from her.
- 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 as a way to resolve an inheritance crisis, but then Dorilys starts to get into the idea, and Donal gets used to it
- In The Borgias, Lucrezia and Cesare are always a little too close. It ranges from her saying that she will never love her husband as much as she loves him, to them consummating their relationship on Lucrezia's wedding night to someone else.
- A two-part episode of CSI focused on this. In the first part, she manages to create enough doubt that her brother committed a murder (that he actually did commit) at her own expense, but also leaving enough holes that she couldn't possibly be the murderer either. In the second episode, she murders his girlfriend and frames him for it, partly to get rid of the obstacle and partly because she figures that by visiting him in prison every day, he'll fall in love with her.
- In Degrassi Takes Manhattan there is a rivalry between Holly J. and Fiona for the affections of Declan who is Fiona's twin brother and Holly J.'s boyfriend. Fiona's attitude is "Boyfriends are temporary. Brothers are forever." She has an emotional dependency on Declan and couldn't stand to come second in his life which she makes clear to a whole party of people.
- 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.
- The original version of the bishoujo game Ko-ko-ro... depicts an incestuous relationship between Souji Kuonji and his sister Asuka. Asuka seems more invested in the relationship than Souji; she even fantasizes about marrying Souji and having sex with him before they even leave the church where they were wed.
- The multiple depictions of incest in Ko-ko-ro... within and outside of the Kuonji family caused enough of an uproar that the game was banned from the Japanese market. An unauthorized edited version was later released, in which Asuka and Souji were no longer presented as blood siblings, but instead as stepsiblings. This was further edited when the game was adapted into a 2-part OAV; here, Souji is shown in flashback to have been an orphan adopted (and later molested) by the Kuonji family.
- In BlazBlue, it sure sucks to be in Ragna's shoes for having a younger brother Jin who not only wants to kill him, but also obsessively lusts after him to the point that he will inflict physical harm or even kill those who he deems will take his "nii-san" away from him e.g. Saya and Noel. However, it's also implied (to the point that it's all but outright stated) that Jin's obsession isn't natural: it's a product of being utterly Mind Raped by the Big Bad, Yuki Terumi, who needs Ragna to hate him as much as possible for as many reasons as possible so that he can continue living. Also not helped by very weapon he wields; Yukianesa, a Nox Nyctores that amplifies the user's emotions and especially their psychosis. Thankfully, Jin gets a hell of a lot more stable after mastering his sword and a few Break the Haughty moments come his way. Still wants to kill Ragna, but he's not lusting over him anymore unless it's a Gag Reel.
- On the other hand, Ragna's other younger sibling Saya is heavily implied to have this for him as well. In addition to him being one of the few positive influences she's had while growing up, she's the template for all the Murakumo clones (Lambda, Noel, and Nu), which all carry fragments of her consciousness and are clearly attached to him to certain extents. Even Izanami, the Goddess of Death, who is possessing her body notes that her feelings for him are extremely strong.
- In the The Legend of Heroes: Trails of Cold Steel, Elise Schwarzer has a crush on the main protagonist and playable character, Rean Schwarzer, who happens to be her brother. Her adoptive brother, though, so it makes it a bit less squicky. Though in the drama CD their mother is clearly trying to hook up her biological daughter with her handsome adopted son. Also, Princess Alfin is heavily into the idea, but unfortunately Rean is pretty Oblivious to Love when it comes to her. He does pull a My Sister Is Off-Limits! a couple of times, but not because of any romantic attraction towards her.
- Never actually happens in Little Busters!, but Kyousuke jokingly references this trope a couple of his nicknames for when Rin loses against him:
Kyousuke: This will be your name from now on: 'Her first crush looked like her older brother!'
Rin: I don't want that, moron!
- 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 that has no "Good End". Either Shiki dies (the True End), or she becomes a vegetable (the Normal End). A side-story in Kagetsu Tohya following Akiha's True End reveals that he is still alive, though.
- Ange Ushiromiya really seems to border on this in Umineko: When They Cry, which is parodied in the side stories of Tsubasa and the various manga omake. In the manga of Episode 4, she makes a complete fixation on Battler whenever she remembers her family. The implications are probably attenuated by the fact that Battler left the family shortly before her birth (and, indirectly, because of it, though he still adored her) and only visited her on her birthdays before coming back to the family and "dying" in the Rokkenjima incident, so they didn't have much of a brother-sister relationship (she was only 6 years old at the time). There is also the fact that she's "only" his half-sister. Until we learn that Kyrie is Battler's real mother, so they are actually fully blood-related.
- Sayu Yagami 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 Suzy 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".
- Even The Simpsons seem to play a bit with the "she doesn't want to lose her brother" model. When in the episode "Milhouse Doesn't Live Here Anymore", Lisa cries because Bart prefers to spend time with his friend Milhouse, later she is very angry with her brother. However, she hasn't shown a similar reaction at any other time.