Tenant refusing to vacate the rented premises what action can I take

My grand mother rented two rooms to a family at about 40 years ago, the tenant died many years ago and now his son along with his wife and 3 children are there. They have two more houses where the other family members lives (along with the wife of tenant), we tried many times to get those rooms back but they always refuse to do that, we have only one room set, we r six members in our family, we both brothers and my sister are upto the age of marriage but couldn't get because of this issue, and can't effort the price they are demanding, every time when we use to talk to them they started abuse