I think it's trying to say that even if you try to destroy Jayjay Jester or destroy the books. It will still kill you.

You can't escape it. Even leaving it alone results to yout sibling dying. Imagine if your brother or sister just died. For real. What would you feel?

There's nothing you can do. The only thing to stop him is to turn the game off. But like in the burned ending, he's trying to escape out of the screen to kill you in real life.