That's quite harsh..

Then your relationship with your bf doesn't seem so secure if an outsider can cause a breakup, so go for it!

I think we need some more background info on this. We don't know how old OP is, if the b/f still lives at home, or what the sibling was doing. For all we know if the b/f lived at home the sibling could be making nasty remarks,making up lies to feed the family or b/f, or maybe even damaging possessions OP may bring over. There's too many "what if" scenarios to throw a ydi and accuse them of not loving their boyfriend/ex now.

While I don't think it's right to break up with him because you hate his sister, I hope you at least explained to him why you were breaking up so he'll know he didn't do anything wrong

Obviously you hate her more than you love him

I feel the same way about my boyfriends mother. She's crazy.

Are they Lannisters?

if his sister could get in the way of your relationship, it really prob wasn't gonna last anw. might as well separate peacefully and continue being friends ?

I'm gonna go out on a limb and say it's cause you are young and both you and your boyfriend still live with mom and dad and you have to deal with his sister every time you go see him. I can't foresee this being a problem if you two live together and don't see her often. I wouldn't use one bad experience at thanksgiving or something like that as an excuse to break up. Explain the situation to your bf first, without intending to break up right there. You're dating him not his sister!

That's kinda low OP dumping him because of his little sister? Really?