A has size as an advantage now, but C is a tough chick and will only get bigger and stronger, so he better watch out. In the meantime, he's just performing his older brotherly duties.
Both kids love to dance (what youngsters don't?), and C really gets her booty moving when Madonna comes on. Even when she can only faintly hear a Madonna song playing in another room, she'll stop what she's doing and start shaking her groove thing.