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. Compare the much less questionable Big Brother Worship.
No relation to Big Brother Is Watching.
- 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.
- Code Geass has it's own page on the incestuous subtext between siblings, with Nunnally and Lelouch being the most obvious example.
- 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 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.
- According to Word of God, Kari had incestuous feelings toward Tai in Digimon Adventure and the conflict between her and Koromon over Tai trying to return to the digital world was deliberately written like a Love Triangle. She seems to have grown out of this by season two.
- 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.
- From the Nasuverse is Azaka of The Garden of Sinners, 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.
- 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.
- 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."
- Belarus from Hetalia: Axis Powers 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.
- The Hidden Dungeon Only I Can Enter has Noir's younger sister Alice, who openly, and happily, will do erotic stuff with him, even engaging in a bit of Casual Kink, always ready and eager for it. While Noir's father has caught on, and is rightly worried about it, the rest of the family, including Noir himself, just happily shrug it off as "normal brother and sister affection," calling the outbursts from Noir's father as "strange misunderstandings," at best.
- How to Treat a Lady Knight Right: Played for laughts in how humorously obvious it is that Houli Dent's little sister Anri is a bit weird about him. Even Leo, generally ignorant in affairs of the heart, internally thinks that of her. Anri tends to cling to Houli tightly and her first impulse upon meeting Leo is to taunt her and, later, challenge her to a fight to stay away from her big brother.
- Hybrid × 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.
- 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.
- 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.
- 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.
- Defied in Kaguya-sama: Love Is War, where Kei deliberately avoids any action that could be construed as her having a brother complex. This is part of the reason why she tries to hide her genuine Big Brother Worship of him, since the two tropes can often be mistaken for one another (that, and she's currently in her rebellious teen phase).
- 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 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.
- My Next Life as a Villainess: All Routes Lead to Doom!:
- Keith has been in love with his adoptive older sister Catarina since soon after they met, something which their mother supports as she feels that Catarina would be an embarrassment to the family if she actually went through with her arranged marriage to Prince Gerald. Of course, Catarina has a density approaching that of a black hole, so she thinks that he only views her as a Cool Big Sis.
- Sophia was supposed to be in love with her older brother Nicol, as was the case in the original timeline, but she also falls in love with Catarina (though she is the least aggressive member of the harem and spends more time trying to hook her up with Nicol than she does pursuing her).
- 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 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.
- Penguin Brothers: Not between siblings, but Hina harbours a childhood crush on her uncle (her mother's much younger brother), Kyo, who grew up with her and became her Parental Substitute after her mother's death. She acknowledges that she can never get together with him due to their familial relationship and that she'd have to move on from him eventually, but even though she has some Ship Tease with two of her school mates, she still chooses to leave the school to accompany Kyo when he decides to move to France at the end of the series, giving her No Romantic Resolution with either of her suitors.
- 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.
- Nanami Kiryuu from Revolutionary Girl Utena deconstructs the trope. She has a very clear fixation on her older brother Touga, and tends to be rather merciless towards anyone who gets in the way of that. She is so obsessed with being her onii-sama's sole target of attention that she got rid of his pet kitten when they were children, and she later humiliates a girl from her Girl Posse who's in love with him. As Touga is gradually revealed to be a Manipulative Bastard who never shows any real affection towards Nanami, her hopeless devotion to him becomes quite tragic, especially since all of her feelings of superiority hinge on her status as his sister. 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.
- 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.
- 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.
- Spy X Family: Yuri Briar has an unhealthy attachment to his older sister Yor, who raised him when their parents died, to the point of trying to fight her husband Loid. He even contemplates abusing his power as a member of the Secret Police to get Loid out of the picture (ironically, he'd have the perfect excuse for that if he knew Loid was actually a spy).
- 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.
- Many characters in Tenjho Tenge remark on Maya's Big Brother Attraction regarding Shin. It's almost to the point of BrotherSister Incest.
- 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.
- 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.
- 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.
- 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.
- Inverted in YuruYuri 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.
- 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.
- Mob Psycho 100 has no shortage of examples of Ritsu really, really, loving his big brother. Fics tend to have him get progressively more unhinged as time goes on. A good example of this can be seen in Obvious You're Meant For Me
- Fate/Harem Antics: Illya makes no effort to hide her attraction to her brother Shirou. Though Shirou is adopted, and had no idea he even had a sister until Illya showed up and tried to kill the girls who were standing too close to Shirou. And then of course there's the fact that Illya is actually older than Shirou.
Illya: It's a sister's duty to take care of her brother, isn't it?
Shirou: That's definitely not what taking care of your brother means.
- the The Loud House fandom tends to employ a gender swapped version of this whenever Lincoln is shipped with any of his older sisters, which actually happens quite a lot.
- 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 Earth's Children series, Joplaya is in love with her older half-brother Jondalar. In her defence, due to the way her culture thinks about reproduction, they are considered 'close cousins' rather than siblings, so she's technically unaware he's her brother. note They also weren't initially raised together, with Jondalar coming to live with their father when they both in their early teens (so the Westermarck effect may not have kicked in). That being said, a relationship with him is still considered taboo on account of them being 'close cousins'; Jondalar also does not return her feelings in the slightest.
- 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.
- 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 Fire Emblem: Genealogy of the Holy War, Lachesis is a proper young Ojou who can't help but be disappointed in men when none can compare to her perfectly noble older half-brother, Eldigan. While this sort of Big Brother Worship and its associated implications isn't unusual for Fire Emblem, the explicit suggestion of incest isn't - if you visit a particular village in Agustria, you'll find that the commoners gossip that they must be having a salacious affair, and in the second generation, Lachesis' daughter confirms outright that she was in love with him. His feelings on the matter remain ambiguous; while he does return her attraction in the official manga, most fans do not take that as canon.
- 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.
- 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.
- 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.
- Never actually happens in Little Busters!, but Kyousuke jokingly references this trope in 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.
- Minimandy from Grim Tales from Down Below is eventually revealed to have feelings for her older half-brother Junior.
- Sayu Yagami in the original Death Note Abridged by TioH and Dargonakis. Who isn't particularly subtle about it.
- Played for laughs at first in Sword Art Online Abridged; Leafa hits on Kirito in Alfheim Online, only for him to tell her his username just as she's about to log out. Back in realspace, Suguha screams in outrage that her brother Kazuto was in the game, and then in disgust over her flirtatious behavior with him.
- In The Amazing World of Gumball episode "The Dress", Gumball is made to wear his mothers wedding dress to school after his clothes are ruined. This leads to his adoptive younger brother Darwin developing a borderline romantic obsession with Gumball in a dress, which only becomes clear to him when Darwin invites him to a rollercoaster and kisses him.
- 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.
- On Duncan Ville, Duncans adopted sister, Jing has a Precocious Crush on him, much to his dismay. Eventually to simply entertain her, they stage a fake wedding, but this causes Jing to behave like they truly are married and becomes a Clingy Jealous Girl towards Duncans crush, Mia. Eventually, she realizes that she prefers to have him as a brother rather than a husband.