Let me say this: when I was pregnant, we planned on the two of them sharing, but after having lived with both of them I have some concerns. My concerns about them sharing are 1) Waking each other up. If on occasion she would wake to nurse at night, she would wake him up. Or during nap time, he plays and talks for an hour before falling asleep. She would never be able to nap in there. 2) My son can climb out of his crib. This worries me that we would go over and bother her or even attempt to climb in her crib which is not safe especially b/c he likes to hit her unfortunately.
This would be my biggest concern. I wouldn't want to leave them unsupervised for long periods. Until he can be trusted, I would make some other sleeping arrangement. If you are all still comfortable with her in your room, why not maintain that arrangement for a little longer? 7 months isn't that unusual for co-sleeping.
I grew up mostly sharing a room and sometimes even a bed with my sister who is 3 years older than me. We shared a closet, dresser, and desk.
When we were younger it was kind of reassuring to have her nearby but we would also keep each other awake at times or fight over the space.
It was most difficult when she was a teenager and we had absolutely no where else in the house to go for privacy. She was unfairly angry and resentful toward me. Having our own room was not an option.
I think the experience taught me to share my space. When I went to college it was pretty easy having a roommate.
I was always much happier having my own room though and I would not make older children share a room if space wasn't an issue. If they had to share I'd try to ensure they each had a private space of their own somewhere.
Some people just need their own sleeping space more than others though. My dd would be unhappy sharing a room with anyone because she is so sensitive to noise. She has to have the radio on at night to drown out any sounds. She has always had sleep issues that would make sharing a room difficult. If another child came along neither one would be sleeping if they had to share that space.
Kim ~mom to one awesome dd (12)
I have two girls that are fourteen months apart and they absolutely cannot share. Their fighting makes the whole family miserable. However, I have two little kids, 4 and 11 months that share currently and it works for now.