Wife is torchering like hell. How to proceed ?

My brother married to a girl in the year 2011. From that day she never give respect to my mother or brother. My father died in 2005. We r 3 sisters and one brother.bothe my brother and his wife r working in software in high tech city hyderabad. From day 1 my brother is adjusting with her. He tried a lot to convince her to be good with my mother. They blessed with a son. SHe never cares about her son. She won't give bath, don't feed and she is not bothered about her son and even my brother. She is earning more than 1 lakh per month. She never spent a penny for this family. All the purchasings , paying bills paid by my brother. He has to pay for her shopping bills also. When they go to their jobs daily, my mother is taking care of her grand son. Once in 2 days she fight with my brother with some other reason. My brother and my mother only taking care of his son. We r so much worried about him. Can u please guide us what is the legal action to apply for divorce.