ANSWER:

He should have moved out right after he got married because Allah has given the right to women to ask their husbands for a separate accommodation after they get married.

Better late than never! Let them live their lives without any intervention from the in laws. 

QUESTION: I have a sister in law she has only been married to my brother for hectic 2.5 years and in those years she has made my mum suffer by making my brother constantly get angry at my mum. He will get his own home but he never wanted to leave home and made that clear when he got married but now has to due to his wife behaviour. please advise.