regarding land which was sold in 2006 in which civil suit pending

sir/madam my late grandfather purchased a land of 7 acres from his maternal uncle (deed 19A) in 1984 and a house in tamilnadu in 1982.He was a doctor.He has 2 legal heirs one is my mother and other is my uncle.He died in 96.In 98,my uncle sons put partition suit of both land&house.1.In 1997,my uncle separately sold 2.3 acres of land to 3rd party.2.while the case is on,my mother &uncle sold remaining 4.69 acres of land to 3rd party informing civil suit pending of 188000 sale deed in 2006.3.Then,my uncle sons got exparte decree order in 2010 of both land&house.4.My uncle sons both went to land party and threatened them that they have 2.34 acres in sold land(of total 4.69 acres).5.Then the land party put cheating case against my mother&uncle in court in 2016.which was going on.The land party ask market value of 20 lakh for cancelling the deed in 2006.kindly give the solution as per law to solve the issue.