Tenant not willing to vacate the room

My mother in law (widow) had rented a portion of a room to Mr. Gupta in 1983, they were paying rent till May 2010 (very low rate). We have stopped taking the rent as they were not willing to increase the rent. So they deposit the rent in court. Now when i am thinking of developing it. I approach them to come to terms and settle the issue. Now they are not willing to sign agreement and pay as per the market rate of the room. The agreement last signed by both the parties was in 1983 only. Mr. Gupta has expired and his son (Vijay Gupta) is looking after the business. I could see that he has three defaulted payment (missed payments) in the court during this five years. I have not received any details of September and October 2015 payments also. Mr. Vijay had also given a portion of the rented room to some other people and they are also not willing to vacate the room. They say Mr. Vijay Gupta's family owe them and will leave only if they are paid. What all is my mother in law rights as a landlady?