Need suggestions against tenant

Respected Sir, I need a advice from you. Before starting any legal action against our tenant. I have a house and with that one tenant. They are living with us for 30 years. My son, recently married. For these I need to vacant my tenant but they refused. The original tenant Mr.A, died in 2012. Now tenant's wife, their son Mr.B., B's wife and their two sons (school students) live here. The original tenant Mr.A had very bad relation with his son, Mr.B. So bad that Mr.A filed a POLICE COMPLAIN against Mr.B (his own son)! After that, his son, Mr.B and his wife and his two sons left our house for more than 2 years. Only Mr.A and his wife used to live. Just outside the legal aspects, just image, how bad it is when a father files a police complain against his own son! After the death of Mr.A, within a week Mr.B (son) with his family returned back and started to live. Since then, no contract was renewed. Also, Mr.B bought their own flat in the same city, Kolkata, and put it on rent. They hinted us that they will leave only if we pay money to them. Please suggest me how do we progress? What is our chance to win the case and dnt give him any money? (pls be honest) How could we handle such a dirty person (Mr.B) for whom his own father goes to police station. Regards