Here are their profiles, side by side, in two different photos:
Their chests are touching, even though their heads are in different directions. Here are their hearts, beating next to each other.
Here are both babies in one shot -- the left of the picture is up, and the right is down. B is very clearly sitting on A's face. :)
Here's my favorite -- a 3-D image of B. (A was face down, so hopefully we can get one of her next time.) I love her big lips, and can you see her foot and toes to the right (her left)?