My girls are the same. Play together constantly, make sure if one gets a drink or a treat that they get a share for the other one too, try to sleep together in the same bed. Very gorgeous. DD2 is now missing DD1 terribly while DD1 is at kindy and we basically have to hang out at home waiting until its time to pick DD1 up again!

I don't know if its a gender thing, or an age thing (they're 12 months apart), but I wouldn't swap it for the world.