Landlord dead without will and successor has not claim succession after death for building on pagadi

Hello Sir, I am staying at mumbai Malad West, I am Staying at chawl system which is on pagadi basis and building was constructed in 1959, the original building was in name of land lady and was managed by his husband. The Land lady and husband have total six children, all was living away in duabai, they did not attended the funeral of her mother and not tooken any care therefore both old couple did not made any nomination or will towards the property building. The Original Land and building is still in name of land lady, all tax bill, water bill, and light bills comes in name of dead land lady. she Expired some times in seventy and old man expired sometime in eighties. We tetant was not aware that building is not succeded by their legal heirs and what law, rules and regulation. Now after this much year when we pagadi room owner gathered to discuss the transform over property we came to understand to one of grand son, who collect the rent and taxes, even collected transfer money from whom who sold their room are not actually the successor as per law even though he is one of legitimate grand son. Now We room owner want to transform this property, how we can go ahead, under which section we file case or affidavit with court so as we can get our rights. We as room owner demand our rights we do not demand any extra. Request to guide us.