Blaire's an idiot!!!! with the games she played with him when he was younger, using him as a tool to hurt Todd, Blaire is reaping what she sowed. She denied Jack his Dad at key times and used those kids as weapons against Todd, with no regard for their best interest.
I do wish that they weren't having Jack be so evil, though. Matthew I could understand, as we've seen that really nasty side of him, but this change in Jack is right out of left field. He was always a hellion, but he wasn't evil. This story would have been more believable with Matthew as the bully, as we've certainly seen the more evil side of him, esp. when he doesn't get what he wants. Plus, with everythign going on with Clint, it could have been a very interesting dynamic to bring out.