Quoting Commander Shepard:" Yes, whether she was keeping it or not. But I can't say that I would let them sleep in the same room. ... [snip!] ... the same room. I know the damage is already done, but I don't think I'd be comfortable and would feel like I was promoting it."
I think I would let them share a room. If they're going to act like adults(getting jobs, staying in school, not being smurftards) then I'll treat them like adults. Plus, I can imagine what that poor girl would be going through. If I were in that position, I would be feeling so alone, I would need to have someone there with me. I can understand why some people wouldn't be comfortable with it, though.