Sharing A Room

We live in a three bedroom home and I have four kids...........guess what, they have to share rooms. No big deal, I am the oldest of four kids we all did it. Right? Well my girls did fine with this, G was 7 when N was born and they did just fine, they would fall asleep together or G would go in later and not wake her. We didnt have any problems until N got to be about 3 and would get into G's stuff.........Now I am the oldest of four so I know how this works and I have handled lots of these problems. G just got her own room for her 12th birthday! Yay! Girls love their own space and she even got a walk in closet (yes, I am jealous)!! We converted a basement room to be hers. Well my boys are a different story...........D was 6 when little D was born so I thought it wouldn't be so different, but I was way wrong!! I cant seem to get them to go to sleep at the same time for nothing!! And if I put little D to bed first and then D, he wakes up his brother every time! I have no idea what I am doing wrong! Why is it that the girls were so much easier than the boys are? And I hope it gets better in the NEAR future because school will be starting before I know it and I dont want to have this issue all year long! And just when I think they fell asleep together, I go to bed to find this!!! Now I have to move them into their own beds before I can even go to sleep.