What's your opinion on this? Are we overstepping? EDIT
Ok, so we live with my MIL(it's not her house it's all of our house) and SIL and DH's uncle(long story). We have 2 DD's that are 11 and 10. SIL is away at college right now and has met a boyfriend(they have been dating 3 weeks maybe). Anyways, she is coming home this weekend and the boy is coming with her. Well, DH calls her last night to tell her that we don't care if the boy comes and stays here, but he doesn't want them sleeping in the same room because we have young daughters, that look up to their aunt, and he doesn't want them getting the impression that it is ok to have boys stay the night and sleep with them before you are married. SIL gets pretty upset and starts saying "Well, Mom let your girlfriends stay the night when I was little" and blah,blah, blah. Well, that's true, but his mom isn't raising our daughters, WE ARE, and this is all of our house and everyone needs to be respected and give and take some. Not saying they can't hang out alone, or as late as they want, but when it is time to sleep, just go to different rooms. I don't think it is too much to ask, so that our girls don't think that it is a good idea to sleep with boys. SIL is 21, if that makes a difference. So do you think we are out of line in asking her to just not sleep in the same room with her bf?
ETA: I am gonna try to answer some questions. SIL has her own apartment, where she lives full-time, while at school.I say this is her home because she is welcomed here to visit whenever she wants. Uncle has Down Syndrome and he lives with us because he can't live on his own. DH, MIL and I pay all the bills for the home. DH's name is the only one on the lease.