Lended money with no papers by my father to his Brother In law in 1995

In 1995, few people in my town established a college, among whom father's brother in law(mother's sister husband) is one. He had came to our house for amount and father has lended 25,000 for intrest. As college is doing good, he said to father that to be as a partner with him and the same is aware to the college partners and common friends between father and him, father too agreed with that. Years passed, but no penny has been given by him and no response even when asked.He used to say he would give amount during my sister's marriage but started escaping whenever we tried reaching out to him at his home asking for money. Finally when sister marriage had come; a day before he had sent 3lakhs with cousin (not his son) which we didn't accept as we are aware how the college is doing and known from partners too and it is expected to be around 15lakhs basis the profits that the college made. I want my father to get relief from this as such things kill mentally. As there's no documented proof that these are the things that had been agreed, if incase no response received for the final try in asking to his family, I want to proceed legally with support of people in the town as everyone is aware. Kindly help in providing a solution legally. Thank you.