Venu sir, I am not a lawyer, if so I would have given my suggestion. Also you are not a judge, you are an advocate.
Are you saying that his wife's parents are right in staying in his wife's home and not vacating and giving mental torture?
People come to a conclusion that aged persons are always right. Which is not true. Good and Bad people exist in all ages.
Same with parents. Not all parents are true to all children. They exhibit partiality and favour certain children.
Example... In many cases sons are favoured over daughters, mother favours eldest son, father favours youngest sons. THese things happen in our society.
I suggest you drop your prejudiced mind and look at presented facts only.