Planning to buy house

Hi , I am planning to buy a house whose owner has died couple of years back. Following is the case /back ground : Father [ Let’s give him name “ABC” ] has given this house to his Daughter [ married & has one kid ] . Daughter dies after couple of years . Son-in-Law [ lets give him name XYZ ] marries to another women [ 2nd wife name say PQR ] . Son-in-Law also died now. Now ABC want to sell this house .He is telling that we need to have Court Registration . Will there be any issue if I buy this house from ABC ?? Who is the care taker , right person from whom I can buy this house ABC or PQR ??