When have a spare room that we use as a playroom. It's connected to their current room by a Jack and Jill bathroom. I figure one day, when we no longer need a playroom, one of them will move into that room. Maybe not. I'll let them decide.
For now, it makes me smile when I walk past their room after they are supposed to be asleep and I hear their little sisterly whispers. I tell them to hush and go to sleep, with no conviction in my voice at all.
Afterthought: It often occurs to me that Gloppy is the only one in our house who has his own room and sleeps alone. Maybe that's why I am never quick to take him back to his room when he makes his way to my bed in the middle of the night.