Well, I have my 6 month old daughter in the same room with my 3 year old son. I put her down at 7:30pm, and my son at about 8pm. (We read his goodnight story in the LR) She usually wakes up between 11:30-2:30am looking for her last nurse of the night and she wakes up between 6:30-7am. I was worried that she would wake my son, but he sleeps through it, no problem. They do tend to wake up at the same time...sometimes if she wakes up early I bring her into my son's bed (he has a full-size futon on the floor) and nurse her and we all cuddle and kind of wake up together, it's sweet. I don't have safety concerns. My son has been very gentle from day one, but in any case my daughter is in a pack-n-play, not a crib, so there's no way he could climb in there, or "swat" her or anything, anyway. Also, we have a small house and I hear them both if there's any stirring. I think I'd have them in the same room even if we had a bigger house, because they seem to like it. You can always try it and see how it goes, and how you feel. If you have safety concerns, obviously I wouldn't do it. One more thing! I was co-sleeping with my son from the beginning, and now that his sister is in the room with him, he is okay with me in the room with daddy. There are nights when he comes to find me and I bring him back into their room, and sometimes I fall asleep in there...so I guess, for me, that's another reason I feel very comfortable, I'm close to them either way. Just wanted to add that!