Rent arrears dispute with a previous tenant

Hi, . I've an ancestral property in my father's name in a small town in TN near Bangalore. My father died in 2009 suddenly. After my father's death, my paternal uncle lent out my property to a small educational institute without my consent and knowledge. Since I was residing in a metro during that period, and since my father's second wife was looking after the said property(at least that's what I believed), I did not visit the said property regularly as I was very depressed after my father's loss (I had anxiety disorder and was put on anti-depressants by a psychologist). When I finally came to know about the educational institute operating out of my house, I confronted my step-mother, uncle and the owner of the institute asking them about the rent and legal rent agreement document. Now, my step-mother says that she too was unaware account the rent-out and my uncle lent it on his own will. When I asked my uncle, he was evasive about the rent agreement and that the tenant didn't pay rent for more than two years. He played with me saying that the tenant was a local goonda and so he was unable to collect the rent amount. The irony here is that my uncle had entered into a lease with the same tenant to use my uncle's vacant land adjacent to my house to build a makeshift laboratory for the institute. People around informed me that my house served as the office and my uncle's vacant land as classrooms for the students of the institute. Once I started raising the issue about rent, my uncle silently talked the tenant into vacating my house, while still running the lab on my uncle's vacant plot. What more, with no electricity, the tenant had been using power from my house to run his lab on my uncle's plot. Again there's no authorization from me to extend power connection from my house to his plot. I feel that my uncle had usurped the advance and rent amount from the tenant. My step-mother might also be playing along with my uncle as she stands to gain from a secret deal with him. In this backdrop, with no legal proofs of the tenant's occupation of my house, how can I present a winning case before an Indian court to avenge my loss? What legal documents can I gather from gov't departments (like electricity board, Panchayat office, etc.) to create proof of occupation of my house by the said tenant? Will such proofs be acceptable in Indian courts? Please advise if there is any other way to fight for justice with legal proofs in my case. Thank you. Regards, Sanjay