I think back to when Carter will still just a tiny one, and how Sean waffled between showing no interest in his sister, and yelling at her every time she made even the tiniest noise. But over the last year, they have really started to develop an amazing bond - you can hardly separate them. Which I'm sure has at least a little to do with Carter's hero worship of her big brother. He's almost got a shadow. Which is great when he does something right, but not so much when he's misbehaving and his partner in crime follows right along.