Dispute Regarding Business Which Was Given Long Time Ago

My father started a business along with his friend. But in the middle, his friend said he wants to discontinue and asked my father to give back his money. My grandfather paid that amount and took control of the shop. My father's elder brother and my grandfather used to run the shop since my father's elder brother had no other work. In return, they would buy lands and give us money occasionally. All of this continued for 15 years. In the middle, there were many disputes and we asked them to leave the shop and we said we would give them their money back since they are looting us. But they didn't give the shop saying that my they have children and had no other work asked the time of 3,5 yrs etc. Every time there was a conflict they used to bypass it by asking time for giving us our business back. My grandfather expired a few months ago. Now when my father asks about the business my father's elder brother says that he developed it and is demanding a huge amount. All licenses of the shop are in my father's name.