My uncle has claimed my father's property

So, my father brought a property in 2008 in Aurangabad, Maharashtra. It's a 1BHK in a prime location. He gave the property to his parents to live as they didn't want to stay with us. Our grand parents invited our uncle and his family to stay with them as they were facing financial crises. My father never took a penny from them as he wanted to be considerate towards his family. My grandmother passed away in 2010 and grandfather passed away in 2019, however my uncle and his immediate family continued to stay on the premises. My father was asking my uncle to vacate the property after our grandfather passed away but he never listened and started avoiding him. This year, my father passed away due to Covid and now we want to sell that flat to pay away our fathers loans and other expenses, however my uncle has denied to vacate the property and is claiming that my father had gifted him the house without any proof. We have all the documents, all the transaction when my father was paying EMI for the flat, closure documents from the bank and clear title on the property. My uncle has acquired the electricity bill in his name, we don't know how. Hence, I want to know what should we do, to make him and his family to vacate our property?