I had one more thought on this. It sounds like the son is being put in a difficult position to choose between father and step father. That's not right. Father should tell son that that is not son's decision to make. The only way this adoption could happen is if the father actively consented to it. He should make it clear to everyone that he won't do that. Back off on the drama and carry on with a parenting arrangement that has been working quite acceptably for many years.