We had our kids share a bedroom for quite awhile. The reason we went to a rental with two bedrooms for them was because one is a boy(older) and one is a girl and at some point it was more appropriate for him to have more privacy. It can be embarrassing if you are sleeping in shorts and things come undone showing your secret parts, you know. Or you might want to change in peace without someone thinking they can come in the door. You also might want some of your own things kept away from your little sis, and you might not want to always have to explain why there are "girlie" things in your room when boys come over to play, etc etc.

Funny thing is, we found lots of rental homes in the Lake City and Ballard areas with one bedroom upstairs and one in the basement. Our main reason for not wanting this setup was that we wanted to be on the same level (floor) as both kids in case something happened--theft, fire, earthquake...but also because there tend to be events less catastrauphic like night of the flu, fear of the dark, wetting the bed, etc and thought it would be nice to hear if the kids needed anything.

Less important, but practically, both kids were afraid of the dark and wanted to be down the hall from each other with a bathroom light, as we had in our first rental home.