I have both my girls in one room (they are 4 and 2 yrs). We have a play area already, and a study, and a spare room, so they don't actually have to share because there's an extra room, but I wanted them to. I think it's good for them. At their ages I didn't think they needed a whole room to themselves. They get along very well and they like being in there together instead of alone. I would do it!