well if he can’t get a good job on the basis of his ability and he got a job in her wife’s family business just because she is his wife and not because he was qualified enough for it then that is really an ehsaan on him from her family.
thats why I said he should change his job and get the one which he truly deserves based on his qualification , experience and abilities.
However , before things get bad speak with him too and your parents too and request your parents to treat him with respect and request him to treat your parents with respect.