I think them witnessing him abuse their older brother and mother with their own eyes is what turned them against him. A man who has to live on a movie set because he pays 10 different lawyers and PR doesn’t have the type of money you think he has.
I really think Angelina turned those kids against their pa. He should leave them out of the will, especially cuz Ms. Jolie spent her considerably-less-BradPitt-fortune, on attorneys.