Bussiness problem

3 years ago

Since last 30 years my father is having a bussines and being elder person in a family he allowed his brother to work along with him without any on paper aggrement of having him as a partner in his firm though they both dividing the income share.
But from last 1 year my father's brother have moved out of my fathers bussiness and started the same bussiness on his own.. being in a bussiness partnership there were some debts they both had taken jointly but since all of those transactions was in cash so now he is denying to repay his share what should we do ??
I had seeked the person who lended them money and asked him to collect the half of the loan amount from my father's brother as well but now he is forcing my father to repay all of that debt though he was accepting that loan was given on family trust and my father's brother had came to collect the money for bussiness.

Please I request you to guide me a way how I can come out of this debt trap in which my father is stuck. I know my father did a biggest mistake by not doing the legal aggrement with his brother. Please guide me.