Advice about boyfriend's relationship with sister

[Charlie Boy II]

I've never heard of anything like that. I have a sister a year younger than me and even the thought of patting her on the behind makes me want to vomit. I mean I can see that she is attractive looking, but as far as I'm concerned she is an asexual entity, like a plant.

[lesa]

Actually it's quite the opposite. His sister is probably the most intelligent person I have met for her age. She's first in her class (she's a senior in high school). The thing is my boyfriend has two sisters. His older sister (the senior in high school) acts this way with him, so he jokes with her back. His younger sister is 16 and doesn't joke like that with him but she's very close to him as well. His older sister also jokes about my boyfriend and I having sex. She always jokingly asks him if he raped me last night. I feel like she just likes talking about sex and she's not really shy at all around her brother.

Sorry to say but there is something definitely wrong. Either she is jealous of your relationship with her brother and this is some psychotic way of express it and get information about your sexual life or she was abused by him or had detailed sex play with him.

I have 2 older brothers and never ever ever... vomit.

Red flag...keep an eye on it.