History Main / MySisterIsOffLimits

->'''Chandler:''' Look, it's my wedding day, okay? If you were getting married I would never do alelonything to upset you.\\

->'''Chandler:''' Look, it's my wedding day, okay? If you were getting married I would never do anything to upset you.\\

* In the ''Anime/CodeGeass'' fanfic ''[[https://www.fanfiction.net/s/10878822/1/The-Japanese-Are-Already-Dead The Japanese Are Already Dead]]'', Lelouch is this to his sisters Cornelia and Euphemia, something he can back up thanks to becoming the Emperor of Britannia. When he discovers that Guilford has Cornelia's handkerchief, he quickly grasps [[LadyAndKnight the implications of the two being together]] and arrests Guilford before attempting to have him dishonorably discharged of his rank until Cornelia knocks him out. And when Suzaku tells Lelouch of his plan to propose to Euphie after years of dating, Lelouch pins him to the wall and tries to recruit Cornelia's help in getting Euphie away before the more fit knight knocks him out.

* In the second part of 2023's ''Film/{{The Three Musketeers|2023}}'', Aramis (Creator/RomainDuris) is very protective of his {{Naughty Nun|s}} of a sister, Mathilde. He's not happy to learn that a soldier got her pregnant, and when he goes after said soldier, he offers him to either [[ShotgunWedding marry her]] or [[ThrowingDownTheGauntlet fight in a duel to settle the offense]]. The matter is settled when the soldier is immediately killed by a lucky cannon shot from La Rochelle. Then later at the end, Porthos tells Aramis he wants to marry Mathilde, which, while not ideal, seems like a better deal to him.

* ''Film/ThirtyMinutesOrLess'', among other things, has the protagonist reveal to his best friend that he has slept with his twin sister. The friend is pissed, as he reasons that sleeping with one twin is the same as sleeping with the other.

* In ''ComicBook/{{Supergirl}}'' fanfic ''Fanfic/HellsisterTrilogy'', Franchise/{{Superman}}'s first reaction when he finds out about his cousin dating Dev-Em is beating the latter up. Since pummeling Dev pisses Kara off, though, Kal-El has no option but to grind his teeth and accept their relationship.

** Similar to canon, Franchise/WonderWoman is extremely protective of her adopted younger sister, Donna Troy. When she notices Conner making heart eyes at Donna, she wastes no time in laying down the law:

* [[https://satyq.deviantart.com/art/Supergirl-vs-Wonder-Woman-551304815 This fanart]] reveals the real reason in Franchise/WonderWoman never hit on ComicBook/{{Supergirl}}'s cousin in the Pre-Crisis DC Universe.

* In ''Franchise/XMen'' fanfiction ''Fanfic/DevilsDiary'', Mastermind lusts after Wanda, but he's too frightened of her brother Quicksilver to try to seduce her.

* There's ''kind of'' a case for Hank Hall and Dawn Granger of ''ComicBook/HawkAndDove''. Dawn is the second Dove, the first being Hank's late brother Don, and he treats her like his sister. So when he suspects Deadman is trying to start a relationship with her, he makes it perfectly clear that she's off-limits. Doesn't stop ''her'' from starting something with Deadman, though.
* ComicBook/{{Quicksilver}} is like this about his twin sister, the ComicBook/ScarletWitch, up until she marries the Vision. It's typically got overtones of a BigBrotherInstinct, but occasionally verges into... less platonic implications. And then there's ''[[ComicBook/UltimateMarvel Ultimate]]'' Quicksilver, who doesn't want anyone dating his sister because... [[BrotherSisterIncest well...]] [[{{Squick}} yeah]].
* ComicBook/SpiderGirl is a rare female example of this trope, trying to keep her "little sister" April away from her manipulative JerkJock ex-boyfriend.
* ''Franchise/{{Superman}}'':

* Falling under the "extended family" category, Franchise/WonderWoman does not approve of ComicBook/{{Superboy}}'s relationship with ComicBook/WonderGirl. Demonstrated by the time the latter two were kissing in midair and Wonder Woman grabbed Superboy by the collar and flung him into a mountain range.
* In the ''ComicBook/XWingRogueSquadron'' comics, Wedge Antilles hasn't seen his sister since he was eight years old, and in that time she's actually become a famous holofilm star and married the [[AcePilot best pilot in the Empire]]. Said best pilot in the Empire [[DefectorFromDecadence defects]] with the caveat that Wedge help him find and save Syal, who went into hiding. Wedge goes to some of his pilots and tells them that they're going to go and save Fel's wife, the actress [[StageNames Wynssa Starflare]], who is also Wedge's sister; he seems okay with her being HappilyMarried to Baron-[[ColonelBadass Colonel]] Soontir Fel, but this trope comes up anyway.

* In ''WesternAnimation/NextAvengersHeroesOfTomorrow,'' four of the protagonists were raised together by [[Comicbook/IronMan Tony Stark]], but Francis[[note]]son of ComicBook/{{Hawkeye}} [[WordOfGod and Mockingbird]][[/note]] was not. When he explains his decision to join their team:

* ''Beaufort'' by Ron Leshem. One of the soldiers is embarrassed because his best friend had started dating his sister and insists on telling the entire barracks just how good she is in bed.

* ''[[https://archiveofourown.org/works/35091475/chapters/113577712 The Dragon's Son]]'': Kagami scares off anyone that tries to asks out [[CrossoverRelatives her cousin Izuku]], and says they would have to beat her in a duel if they want to date him. Justified as Izuku ''is'' embarrassed that strangers are trying to date him and is too awkward to say no, so he's grateful that Kagami is turning them down on his behalf.

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* ''Manga/KaguyaSamaLoveIsWar'': Fujiwra is completely against the idea Shirogane dating her little sister Moeha because all the trauma from the times she's had to tutor him. That said, Shirogane isn't even aware that Moeha has a crush on him and almost certainly wouldn't be interested if he was as his feelings for Kaguya are practically at SingleTargetSexuality levels.

* ''VideoGame/BlazBlue'':
** The game has a female example in the form of [[LadyOfBlackMagic Nine]]. Nine is '''''very''''' protective of her little sister [[NaiveEverygirl Celica]] and if she so much as ''thinks'' you're trying to hurt her or fool around with her (and yes, being a [[AllMenArePerverts male]] in Celica's presence is all it takes to make her think that), you better hope Celica or [[HeterosexualLifePartners Trinity]] can call her off. [[spoiler:This gets more serious later when it's revealed that a way to stop the Black Beast would be to use Kushinada's Lynchpin. But as doing so would mean sacrificing Celica, she decided to create weapons called Nox Nyctores from countless souls. She does feel bad about the sacrificed souls, though]].

* Three examples in ''WebVideo/CriticalRole'' -- two of them have Vex and Vax pulling this with the other's developing lover (though Vax had a legitimate excuse after [[spoiler:Percy's [[FailedASpotCheck failed Perception]] resulted in Vex's death]]), but they eventually become [[ShipperOnDeck shippers on deck]]. The third sticks -- Scanlan backs off of [[spoiler:Percy's sister Cassandra]] when he does not approve of his attempt to impress her.

* ''ComicBook/{{Asterix}}'': Carferrix's attitude to his sister Chipolata in "Asterix in Corsica". HilarityEnsues when a Roman officer shows up at the door and demands to search the house. Carferrix orders Chipolata back indoors before she can even answer him, and proceeds to accuse the Roman of 1) talking to his sister, 2) not liking his sister, 3) ''liking'' his sister, getting progressively angrier until the officer runs for his life. For a moment, it seems he was just pretending to frighten the Roman away (since he was, in fact, sheltering three enemies of the state). He then turns around and scolds Chipolata for "flirting with Romans," clarifying that nope, he is a murderingly overprotective brother.

* GenderFlipped in the ''Manga/DeathNote'' [[AlternateUniverseFic AU]] ''{{Fanfic/Seigikan}}'' when Light notes that his sister Sayu gets scary protective of him when he admits [[VillainsNeverLie the (technical) truth]] that he got beat up by [[CrazyJealousGuy one of his jilted lovers]].

* GenderFlipped with the one being off limits the younger brother in the ''VideoGame/TalesOfTheAbyss'' ''Fanfic/{{Reflections}}''. Asch is not entirely pleased about Tear's interest in his "twin" Luke. {{Downplayed|Trope}} in the end, as he ultimately accepts their relationship, but he's still obviously worried about Tear inadvertently hurting Luke.

** Note that [[spoiler: She's in junior high]] It's that kind of song...

* Music/VictoriaJustice's music video [[https://www.youtube.com/watch?v=ven3UgzswBo Best Friend's Brother]], about her huge crush on her best friend's older brother. She {{defie|d}}s the {{genderflipped}} trope, hoping to keep her crush secret from her best friend. Her {{defi|ed}}ance is only [[DownPlayed expressed in a few lines]].

While the title says "sister," variations of it also include [[YourMom mothers]] and other female relatives (such as cousins), and for girls, the GenderFlipped "My ''Brother'' is Off-Limits." This doesn't include daughters or sons, because BoyfriendBlockingDad and MyBelovedSmother, respectively, already cover those. Exes fall under TheBroCode instead.

->'''Chandler:''' If you were getting married I wouldn't do anything to upset you.\\

-->-- ''Series/{{Friends}}''

* The main ThreeAmigos of ''WesternAnimation/AvatarTheLastAirbender '' is of the brother and sister + a friend variety. Friend Aang ends up marrying the sister, Katara, but this is only ever really brought up once. In the episode “The Fortune Teller”, Aang eavesdrops in on Katara getting told she’s going to marry a powerful bender. The episode is pretty early in the series, but he’s been harboring a crush since he met her. He decides to make a move and go to the brother, Sokka, for advice because Sokka is a few years older than him. A classic OneDialogueTwoConversations ensues in which Sokka thinks that Aang is talking about one of the girls that lives in the town and Aang thinks Sokka is giving him blessing about liking Katara. Aang even asks him, “You’re okay with it?”.