This has been on my mind about the case. I believe Kitty and Jose abuse, their children as a form of control over their own inner turmoil about their childhood abuses. Kitty saw what she hated in Jose in Lyle, Jose saw weakness in Erik and an eagerness to be loved, just like Kitty.

It's like they made it into a strange sick game, when they were hurting the children individually it was a rush. When they were hurting the children together, I mean the making fun of Lyle for bedding wetting, the stuffed animals, murdering their pets, Kitty and Jose were at their happiest.

They wanted to snuff out any innocence that Lyle and Erik had because they didn't have it in them. They were just monsters.

What do you think??