We put the girls to sleep each night like this:
And most nights when I go to get them up, they are still in those positions. But a few nights ago when I walked in I saw that Claire had turned 90 degrees and had pressed her little bald head up against Grace's mouth. Grace was less than pleased about this. So, I moved Claire back to her regular position and they fell back asleep.
I have heard from more than one person that sometimes twins will instinctively move closer to each other as they sleep. I have noticed this on a few occasions, but I was never sure if they were moving closer to the other one or just moving.
But this morning when I walked in, I saw they had kicked off their blankets in favor of a little body heat.