Land related issues 9194713754

My father bought twenty decim land from my uncle. However, it was not registered. He gave money thinking he was close and loyal and there are many witnesses to this. The land has been in my father's possession for about 15 years. But later his uncle refused to sell it. He also denied taking money. He died a few days later. After that the heirs could not come to any conclusion. At his janaza, a man stood up and said that the deceased had bequeathed to him some land (to my father). Tell the children to take it. As a result, we have a conflict with them. Now my question is, what is the right solution in the eyes of the law? I would be grateful if you could let me know. 5189869213