Occupancy of tenant after death

Hello, I am having my own house in Kolkata. We are a family of 8 and the house is in my father's name. We have a tenant in Ground floor of the building since last 40 years. Now the person who signed the contract has passed away. His wife is dead before and his only daughter is married and stays with her husband is husband's house. Now his nephew who used to stay with the tenant is claiming right to stay in my premises since he was associated with the tenant for long. As on date the premise is lying vacant. In case we refuse to accept rent he is threatening to deposit rent in the rent controller office. Now I have 2 questions: 1. Can someone who is not legal heir of tenant can claim tenant in his name? We have not signed any tenancy document with the nephew. 2.In what way we can claim back the portion rented out considering the tenant has no legal heir claiming the premises.