Gracie & Ava are always getting together for some reason - usually because one of their mom's has something to do that would bore them. When I had to help them up the stairs I would say "one girl, two girls" as I took their hand or picked them up. Now, they've taken to saying it in place of "me too!" If you give one a handful of raisins, the other will pop into the pantry and say "Two girls!"
They're pretty good at sharing for being two and the baby of their families. Still, sometimes it comes down to "You has to share!" and "No! Just one girl. One. Girl."