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Charlie is attracted to Alice, and she shares his feelings. Unfortunately, Alice is Bob's sister, and Bob and Charlie are the closest of friends. As such, Charlie feels it's wrong for him to date Alice, no matter how much he wants to.

A major Truth in Television trope, as most any guy can tell you. If you've known someone for more than 24 hours, his sister is off limits. Forever. Some reasons behind this are:

  1. Whenever Charlie sees Alice, he can only think of Bob.
  2. If Charlie and Alice do break up, his friendship with Bob may be over as well.
  3. Bob is actually okay with it, but has delivered an epic If You Ever Do Anything to Hurt Her... speech, and Charlie doesn't want to take that risk.
  4. Charlie (and in some cases, Bob) may have a history of being, shall we say, "less than respectful" of their... "conquests" and Bob doesn't want his sister getting the same treatment.
  5. Bob is overprotective of Alice and doesn't want anyone dating her, and Charlie doesn't want to antagonize his friend.
  6. Bob is creepily jealous of any guy who gets close to his sister.

This may also be a symptom of a character having a Big Brother Instinct, if Bob is angry at Charlie for dating Alice, but Bob and Alice aren't actually related, or are just friends.

Could lead to a Knight Templar Big Brother.

Note that while the title says 'sister', this includes mothers, brothers, cousins, and even more extended family. Except daughters, because Overprotective Dad already covers that. Exes fall under The Bro Code instead.

Not to be confused with Brother-Sister Incest. Unless that's why they don't want anyone dating her.

Examples of My Sister Is Off-Limits include:

Anime & Manga

  • In the second episode of Kimagure Orange Road, Kyosuke and his pals (Those Two Guys) are ogling a leotard-clad aerobics class from a nearby restaurant. They soon see that Kyosuke's younger sisters are in the class, and sure enough, Kyosuke almost immediately covers the other boys' leering eyes.
  • If you come out and tell Romano you're interested in his little brother he will flip the fuck out.. Hell, even so much as barely indicate attraction.
  • Death Note: When Touta Matsuda shows interest in Light's sister Sayu, who has grown into quite the cutie, no one is thrilled. Specially, Matsuda's boss Soichirou... her Overprotective Dad.
    • In the manga, L once wonders if Sayu could be Kira. Light screams at that.
  • Frey in Mythical Detective Loki Ragnarok is like this when Freya is around Loki. What he doesn't realize is Freya is doing all the flirting.
  • Komui Lee in D.Gray-man has this bad regarding his little sister, exorcist Action Girl Lenalee Lee. At one point Inspector Link actually blackmails Allen by threatening to tell Komui that he is alone in a locked room with Lenalee. Allen immediately apologizes and opens the door. And when someone was ogling Lenalee, Komui's coworkers gave us this wonderful quote:

 "Section Chief Beck, I would advise you not to look at Lenalee that way."

"Why? Does she have a lover?"

"She has a brother."

  • Inverted in Hayate the Combat Butler. Kaoru takes Yukiji on a vacation during Golden Week and attempts to confess his feelings for her. He doesn't have the courage, so instead he asks if Hinagiku has a boyfriend. Yukiji's eventual response is asking what he likes about Hina.
    • Yukiji is shown to be rather caring about Hina, so it's not quite clear how the rest of that conversation goes.
    • Additionally, there seems to be indication that Yukiji knows about Kaoru's crush on her. So she might just be pushing his buttons (to try and get him to confess normally).
  • Lelouch and Nunnally.
    • Unless you're Suzaku, in which case Lelouch did at one point consider the idea rather valid, and it still may be, despite Lelouch being dead.
  • Inverted in Ranma Half when Kuno, despite otherwise disliking Ranma (most of the time), easily gives Ranma "permission" to date his sister. Ranma never wanted to, and considering how she behaves towards him, and her frequent affinity with paralysis may not have been as benevolent an act as it seemed.
  • In Rave Master, Haru does this trope when he learns of the relationship between his sister Cattleya and Shuda.
    • He did this earlier when, another guy was dating Cattleya and broke up her heart. So naturally, when he saw said guy again, he made every effort to punch him out again. Not to mention Shuda himself when finding out about that guy, he wanted to chop him up to pieces also.
  • The Yu-Gi-Oh! anime has type four, or maybe type five with Joey and his sister, Serenity. This mostly affects Joey's best friend, Tristan, who is nuts about Serenity (while Serenity herself sees Tristan as a friend).
  • Yu Yu Hakusho combines 3 and 4 with Yukina and his brother Hiei. Everyone who touches Yukina, especially Kuwabara, will get disemboweled and burned alive by Hiei.
  • The only redeeming feature of Dallas Genoard in Baccano is his violent reaction to his friends (who, like Dallas himself, are two-bit thugs) ever mentioning his little sister Eve.
  • A reversed example in Infinite Stratos: Chifuyu Orimura is very much aware about the Unwanted Harem that pines for her younger brother, but she makes it clear she's not simply letting them just have their way with him.
  • DO NOT get any ideas of dating Noa's brother in Oniichan Control SHE WILL KILL YOU. This isn't because she wants to protect him of course but because she wants him for herself. (Okay, maybe a little of both, but mostly the latter.)
  • Subverted in Guyver, where Tersuro is pretty much a Shipper on Deck when it comes to Sho and his sister Mizuki.

Comic Books

  • In the Marvel Universe, Quicksilver is like this about his twin sister, the Scarlet Witch, up until she marries the Vision. It's typically got overtones of a Big Brother Instinct, but occasionally verges into... less platonic implications.
    • And then there's Ultimate Quicksilver, who doesn't want anyone dating his sister because... well... yeah.
  • In the X Wing Series 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 best pilot in the Empire. Said best pilot in the Empire 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 Wynssa Starflare, who is also Wedge's sister; he seems okay with her being Happily Married to Baron-Colonel Soontir Fel, but this trope comes up anyway.

 Hobbie: "Why didn't you let us know you had a babe for a sister?"

Plourr: *smacks him* "Idiot, you don't ask that kind of question."

  • Spider-Girl is a rare female example of this trope, trying her to keep her "little sister" April away from her manipulative Jerk Jock ex-boyfriend.
  • Falling under the "extended family" (of sorts) category, Wonder Woman does not approve of Superboy's relationship with Wonder Girl. 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.


  • Scarface does this to a tragic level. Tony is protective of his sister Gina. When he finds out that his friend Manny had been seeing her, he shoots Manny dead without a word. Gina then reveals that the two of them had just been married.
  • The brothers in Fools Rush In seem to be like this, at least that's what Alex fears.
  • In Face Off, this is the source of Dubov's anger at Troy. Later inverted when Archer as Troy recruits Dubov to help him escape by telling him he didn't actually do it.
  • A minor example of this trope from Groundhog Day, when old classmate of cynical Phil Connors bumps into him in Punxsutawney, PA, and is trying to get him to remember him:

 Ned: Ned... Ryerson! "Needlenose Ned"? "Ned the Head"? C'mon, buddy. Case Western High. Ned Ryerson: I did the whistling belly-button trick at the high school talent show? Bing! Ned Ryerson: got the shingles real bad senior year, almost didn't graduate? Bing, again. Ned Ryerson: I dated your sister Mary Pat a couple times until you told me not to anymore? Well?

Phil: Ned Ryerson?

Ned: Bing!

Phil: Bing.


 Private Joker: "I wanna put my tubesteak into your sister. What'll you take in trade?"

Private Cowboy: "What've you got?"

  • The Unforgiven although they become romantically involved later in the movie This is the spirit of the thing in the scene where Johnny Portugal rides up to Ben Zachary's step sister Rachael.

 Johnny: You have a burr in your pretty hair

(Ben proceeds to rip Johnny off his horse, punch him and they stop short before brawling. After things cool down, Ben shouts to everyone present)

Ben: Anybody else see a burr in my sister's hair?

  • A Film Noir called Sweet Smell of Success takes this to a dark extent, in which a reporter ruins the boyfriend's life in order to get him away from his sister.
  • Inverted in Bebe's Kids, where Kahlil and Pee-Wee encourage Leon to kiss their sister.
  • In Lord of the Rings, Eomer did not want Grima Wormtongue near his sister and for a good reason, since Wormtongue works for Saruman and had actively stalked Eowyn for quite some time. In this particular case, Eowyn didn't particularly want Wormtongue anywhere near her either.
    • Although it wasn't really implicit in the films, in the book Eomer does (warily) approve of the man she eventually marries.
  • An all-female and probably non-romantic (despite a storm of Les Yay) variation takes place in Sucker Punch: Rocket is obviously fascinated with Baby Doll and would follow her into a reckless escape attempt. Rocket's Cool Big Sis Sweet Pea (who has a bad case of Big Sister Instinct towards her) is very opposed to them doing anything together and only lets them carry on with her keeping an eye on them. Turns out, she was right: Baby Doll's plan does get Rocket killed.
  • A major factor in Living Will, with Belcher upset about Will and Krista's relationship.


Live Action TV

  • Subverted in Lincoln Heights with Tay and his sister Lizzie. Most (like nearly all) of his friends find her attractive and while he doesn't really care if they're interested in her, he wont play match maker for them either.
  • The Fresh Prince of Bel-Air. Carlton with Ashley. With Will its more of a case of 'My Cousin is Off Limits'. Strangely neither of them care about who their older sister/cousin Hilary dates or sleeps with. In fact Carlton tried to get into university by advising the university rep how to get Hilary into bed and advised her to get out of problems with the IRS by wearing sexually provacative clothing.
    • It's not that strange - Ashley's a teenager, while Hilary's the oldest. There's a reason it's called a Big Brother Instinct.
  • On Saved by the Bell, Slater gets mad at Zack for dating his younger sister, JB.
  • Friends loved this. Chandler dated Ross' sister, Ross dated Rachel's sister, Joey went out with Phoebe's sister, Chandler got with Joey's sister at a party...
    • ...and couldn't remember which one...
      • Joey wasn't upset by the idea, indeed he was ecstatic, until he learnt about the above detail.
    • With Chandler and Monica, Ross explodes at them when he first finds out, until they both say that they're in love and not just fooling around. He immediately becomes happy for them. Of course, he was taking anti-rage drugs at the time.
    • Phoebe even thought about coming on to Ross & Monica's cousin. Female cousin. Who was played by Denise Richards, so that's all right.
  • On Growing Pains, a girl befriends Carol Seaver — just so she can get close to Carol's brother, Mike. Carol feels hurt about being used.
    • In another episode, Mike's friend Boner wanted to take Carol to a dance. Mike was upset at first but later accepted the pairing.
    • Yet another episode saw Mike coming home from school and explaining to his father that he beat up one of his friends. It seemed that his friend told Mike a rumor that Carol and her boyfriend were sleeping together. Mike didn't understand why he got so upset until his father explained this trope to him.
  • Power Rangers in Space did this with the usually Ho Yay-tastic Andros and Zhane. Thing is, little sister Karone was the Big Bad Astronema at the time, nobody knew she was Andros' sister, and the episode where they'd dated was very crack-tastic. It was more of a humor-oriented callback to that episode than actual disapproval. The best part was that they had the argument while sneaking into the enemy base to rescue her.

 Andros: Let me get this straight. You went out on a date with my sister?

Zhane: I didn't know she was your sister!

    • In Power Rangers RPM, Gem seems to disapprove of the potential relationship between his twin sister, Gemma, and Flynn. Of course, this has less to do with his opinion of Flynn, and more to do with the fact that, prior to Gemma's decision to help Flynn with his work, they had been Single-Minded Twins; this romantic initiative on her part meant that he'd have to start forming independent thoughts and sentences.
  • Sex and the City had a gender swapped My Brother Is Off Limits plot regarding Samantha and Charlotte's brother. Samantha of course blatantly disregarded this. What does that tell us?
  • Gus on Psych has a Big Brother Instinct for his older sister Joy.
  • In How I Met Your Mother, Casanova Barney makes it clear [1] that he finds Ted's little sister attractive, and Ted tries to prevent him from meeting her. It doesn't work, but they don't sleep together.
  • Subverted in Full House. Danny isn't at all happy with his sister dating Joey, but finally tells Joey that it's not cause he's worried about his sister, but that he's being protective of Joey. As her job requires a lot of travel, he didn't want Joey's heart to get broken.
  • Subverted exactly the same way in ER. Gallant clearly doesn't want his MS-afflicted sister becoming involved with Pratt, who is something of a player. However, when said sister gives Pratt the brush-off after their night of passion, it becomes obvious that Gallant was trying to protect Pratt from HER, not the other way around.
  • In That 70s Show, Hyde is upset when Kelso sleeps with his half-sister. Eric, on the other hand, doesn't really care when Kelso and Fez sleep with his sister, since she's the town slut.
  • Herman's Head. Herman doesn't like his best friend, Handsome Lech Jay, sleeping with his sister because he still thinks of her as young and innocent when she's definitely not. Lampshaded in another episode where the two are laughing over all the Wacky Hijinks Jay has gotten Herman involved in. "And (ha-ha) remember the time I slept with your sister?" Cue immediate Death Glare from Herman.
  • Mentioned in Stargate SG-1. To verify Daniel's identity after a body-swap, Jack asked him what color Daniel's sister's dress was when he (Jack) took her out on a date the week before. Daniel replies that he doesn't actually have a sister, but wouldn't let Jack date her if he did.
    • Rodney McKay does have a sister, Jeannie, and expresses similar opinions toward his military best friend, John Sheppard.

 McKay: She's married and she's my sister!!

Sheppard: I was just saying hello!

McKay: Sure you were. I've seen that look on your face before, Kirk.

  • Coop's sister in Hannah Montana when she tries to date Jackson. Coop gives him the 'Don't make eyes at my sister' speech. Unfortunately since she's presented as a slut, it loses some of its effectiveness.
  • In NCIS, Di Nozzo asks why McGee didn't tell him that he had a little sister and Ziva rolls her eyes. Naturally no one would tell Tony that they had a little sister...
  • Subverted in Peep Show, in which Jez specifically begins dating Mark's sister precisely because it upsets Mark. While an act of spite to start off with, it soon backfires on Jez when it occurs to him exactly how similar Mark and his sister are — while they're having sex...
  • Averted in the one of the RAF pilots sketches of The Armstrong and Miller Show. One pilot says that he's only the other's wingmate because he's dating the other's sister.

 "She's well up for it."

"Hey, don't talk like that. That's my sister, man."

"But she is well up for it."

"She is, she's slack."

  • Dexter: Without ever stating it out loud, Sergeant Batista heavily implies this to intern Louis when he starts dating Batista's little sister Jamie.


  • As the third page quote indicates, Stephen Lynch's "Best Friend's Song" subverts this. Mark Teich is fine with Lynch sleeping with his sister... he just has to pay first.
    • Note that She's in junior high It's that kind of song...
  • In the second music video for the Black Eyed Peas song "Bebot" does this for his sister Jasmine.
  • Elton John's "Your Sister Can't Twist (But She Can Rock 'n' Roll)," in which he brags about having had sex with a friend's sixteen-year-old sister.

Newspaper Comics


  • In Chaucer's Troilus and Cressida, Pandarus, trying to find out who Troilus is in love with, promises to help him win her even if she were his sister.
  • West Side Story, of course. "Get your hands OFF my sister, American scum!"
    • Except that the above line is directed at an enemy, not a friend, and said sister is actually supposed to be with her brother's best friend, a coupling of which said brother implicitly approves.
  • The song "Don't Tamper With My Sister" from On a Clear Day You Can See Forever, though the complaint here is just that it's in public (and the character is only pretending to be her brother).

Video Games


 Qwark: I thought we agreed to put that unpleasant jungle business behind us.

Skrunch: SQUARK!

Qwark: It was mating season! How could I have known she was your sister?!

Notices Ratchet and Clank are watching

Qwark: How long have you two been standing there?

Clank: Too long.


 Packie: "What a girl! I think she likes you. Word to the wise, though - she don't put out. Which is convenient, 'cause if she did, I'd have to kill you."

  • A mild example from Tales of the Abyss comes in the sidequest where you have to find Emperor Peony's pet rappigs. He's named all of them after people he knows, and the one named for Jade's sister Nephry has the nicest collar. Given that Peony and Nephry have a (long-past) history anyway, Jade is noticeably displeased by this discovery.
  • In Dragon Age 2, Carver's dislike of Sebastian may stem partially from this trope.
    • Alternately inverted, as Hawke has to point out to her sister Bethany that her boyfriend is off-limits.


  • Ryujin of Mob Ties informs Sidney Burns that if he marries Mika, Ryujin's sister, he will kill Sid, in the very first issue. This puts Sid in a bind, as Papa-san, Mika's father, will kill Sid if he doesn't marry Mika.
  • Played with in Panthera, as Jason is clueless about Fletcher taking a liking to Taylor until Kira points it out to him - when he promptly goes into stunned denial of the possibility precisely because Fletcher is his best friend.
    • Now that Kira told him, though, he's a completely straight example of this, with some Knight Templar Big Brother thrown in for good measure.
  • In this strip of Loserz, this trope is invoked when talking about Adam's little sister.
  • Gender switched in Questionable Content where Dora gets very upset about the idea of her friends dating her brother.
    • Two reasons behind this. One being Sven is very anti-commitment and is likely to cheat (Which he does). Second, she reveals to Marten that a lot of girls in high school only pretended to be her friend so they could seduce Sven and she still resents it.

Web Animation


 Coach Z: So your sister and I can— *punch*

    • Also in the DVD-exclusive Sbemail "Family Resemblance." Strong Bad imagines Pom Pom's sister, then imagines hitting on her. Pom Pom is not okay with this.

Western Animation

  • In All Grown Up, Chuckie takes offense when he thinks Tommy has romantic feelings for his sister, Kimi (It's later revealed that it was the other way around, and only for a few minutes, though at the very end it's implied that Tommy and Kimi may actually have a thing for each other after all).
    • Inverted in another episode when Phil actually begs Tommy to ask Lil to dance so she'll leave him alone.
    • Also played straight when Phil chases off a guy talking to Lil when they begin to realize their gender differences.
  • The main character from Danny Phantom is absolutely livid when his older sister is dating a biker named Johnny and spends the entire episode splitting them apart. Of course, he's a ghost who plans to use her body to host his equally ghostly girlfriend, but still.
    • Of course, some of his anger DID seem to come from Jazz acting OOC because of the possession plot, but it was mostly the above.
  • Subverted on Re Boot, where Enzo Matrix's sister Dot is the one with the crush on Bob. Since Enzo idolizes Bob, he doesn't mind at all when they become a couple, and his only reaction is wry amusement when he learns that Dot uses the password "Guardian" for the Mainframe Archives:

 Dot: Activate archival entry.

Security System: STATE NAME.

Dot: Dot Matrix. Password, "Guardian."

Security System: ACKNOWLEDGED.

Enzo: "Guardian"? Dot...


 Francis: Besides, anything to impress a girl right?

James: Girl?... Wait, you mean Torrun? Dude, she's like my sister!

Francis: So... she's available then?

James: NO!


 Hans: I kissed your sister! On the lips!

Skipper: I don't have a sister, and if I did she wouldn't have lips!

Hans: Really? Then who did I kiss?

  • Les to Noam in Rated A for Awesome.

 "Dude! That's my sister!"

  • In the Family Guy episode where Meg turns 18, Quagmire immediately starts to put the make on her. Stewie kicks him in the shins while yelling "stay away from my sis!"
    • In another episode, he runs into Herbert and tells him to "stay away from [his] brother's butt."

Real Life

  • Real Life example: This is actually the story behind the band No Doubt. Gwen Stefani's brother, Eric, started the band and she liked fellow band member and friend of the family Tony Kanal. He thought she was off limits but they did end up dating for a while in secret. The relationship was less than successful as reflected in some of the group's songs like Don't Speak. Everything turned out okay in the end though and she is happily married now and he is also in a relationship. She sang about this in the song Cool indicating that they had closure.
  • Maxim Magazine codified the 24-hour rule (mentioned in the description above) as a "Man Law."
  • Another Real Life example: Zinedine Zidane's famous headbutting of Marco Materazzi in the World Cup Finals came after Materazzi said 'I'd rather have your sister' when Zidane offered to give Materazzi his shirt, which he'd been pulling on. Or something like that.
  • Among some traditional people, like the Maasai in East Africa, it is common that young men of the same age form a group of warriors. They consider the others in the group their brothers and hence, dating a "brother"'s sister is as unthinkable as dating your own.
  1. "It's like listening to Weirld Al Yankovic, if Weird Al Yankovic only sang Christmas carols about banging my sister."