How to revenge

Bonus points if the child becomes wealthy later in life.
That probably won't happen at age 11 though.

Well, you have to do it right at the confusing stage of the child's life. If you wait too long they'll still cherish him as the man who raised them. If you do it at 11, especially if it's a girl, whenever he won't let her do something she will come running to you, eternally frustrating him. MUAHAHAHAHAHA.