Joint Family Property DIspute

Hello all, We have Joint Family till date. My late Grandfather has four sons, my father being the second. All the brothers family stay in the same house having a single kitchen. All properties bought till date (excluding ancestral properties) have been registered with equal share in all the four brothers name. The ancestral property is in my grandfathers name. Recently we purchased one 1500 sq ft apartment property through joint family income. But we learnt later that my, uncle(third son) due to treachery had got it registered in his single name. In this situation my father is losing his share via rental income and also lost the value in the property. When my father seeks his share as even he had contributed his hard earned money, my uncle and other brothers are reluctant to offer him his share. Also my uncle has not enough white money as per Income tax records to purchase the property individually (How can I expose him in black money case?). Please advise in two scenarios:- Option 1 - If he is ready to transfer 25 percent share via settlement in my dads name, what is the process??? (Will gift deed suffice or settlement deed?) Option 2 - If he doesn't agree, what legal action can be taken so that he is threatened and he agrees for the transfer?