D2's movement into D1's room meant more than just more sleep for me. It also focused them as siblings--them on the one hand, and us, the grownups, on the other. We hear them there chattering after they've been put to bed or before we go get them up in the morning. (This is completely fine with us as long as there's no yelling or getting out of bed.)
Maybe it's also that they've had so much time lately to interact primarily with each other, mostly, I'm afraid, because I'm suffering from such a bad case of cabin fever that I would rather not interact with anything closer than the sky. Anyway, they're busy with their own invented games and plays, into which I am only occasionally invited to enter.
Brothers and sisters of a close age, growing up together, spending all day with only as much supervision as a tired mother can spare, have their own world in a way I doubt any other people can have. No one else has so much time or so much curiosity. I set the boundaries of their world; I provide the raw material. But the world is their own.
I don't mind being a grownup to awfully much, but I am a little jealous.