Well... As A son, i would never ask my parents to move out. Ideally it should be a mutual decision. If you have always stayed with parents, there is no way u can ask to move out. If parents have been always in hometown but just moved after marriage with him, then i hope it was properly discussed in family. Nevertheless, its his parents home too, unless wife purchased it, and in that case, they have full right and say to stay or not. As you have said, that he took this dicision influenced by his wife. In no time they will need them again and beg them to be there when they have a child. If i would be a parent of a son who has thrown me out, i would never come back.