Need Help and Suggestions ..

So, let me start in this way , There is a house on the name of my uncle (paternal) unmarried he bought it in the year 2011 from a person x. In 2014 my uncle passed away(died) , when he bought this house it was an old construction seeing that he reconstructed the house before he died . After his death since he was unmarried there are 4 legal heir of my uncle. There was a case going on this house which my uncle didn’t know ,the case started in 2010 where the person Y made a agreement of sale deed with person x to own this house . Later person x didn’t responded to person Y and sold the house to my uncle in 2011 (my uncle didn’t know that case was going on - on this house so he bought it looking at encumbrance certificate). The Case out come was made in 2013 and finally in 2015 addl senior civil judge sent a letter to sub registrar that to register the house for person Y with case(court) documents enclosed . So my Question is how can I Claim back my uncle’s house and acquired possession?