Regarding residential proerty dispute

My grandfather owned a self-acquired residential property in Haryana. He died untestated in 1986. He was survived by two sons (including my father), two dauthers and my grandmother. The residential property (150 sq yards) in name of my grandfather was in possession of my chacha since then. My chacha had been paying the land tax to municipality from beginning. My chacha, aunts and grandmother sold their share to my chachi recently. The residential building on that land was recently demolished and completely built afresh by my chacha and title of property (which was in name of my grandfather) in municipal records was changed in favour of my chachi's name before getting permission for approval of construction but without my father's consent. Now when my father asked for his share in residential property, they are not ready to give that. My father only has a certified copy of the land registry and sale deeds executed between my chachi (buyer) and sellers of respective shares. What steps can be taken by my father to secure his share (1/5 th) in that property.