The contract, I suppose, was a standard one from a laws/contacts database. So don't worry much about the layer father. It might be that father has told the son

The contract, I suppose, was a standard one from a laws/contacts database. So don't worry much about the layer father. It might be that father has told the son what is best to do (to buy all the rights for the copyrighted material), and the son trusted father's authority. I don't know if in your country a vocal contract has any power. Right now you can prove that this material is under your copyright, but he can't prove that he payed you for _all the rights_. So in my legislation system you'd still have 100% of control over the situation.