Ancestral property dispute between siblings

my grandfather bought a 72 decimal tland after gf died my father was a minor n eleder father was the guardian. during road division 16 decimal land merged to road n my elder father got the emoluments. he married three times ..two died without child .third was in Bengal having two sons..he was also living for 50 years in Bengal.my father has been paid all taxes for 56 decs out of 72..for 50 yrs.now elder father also dead..his son appeal for partions n threaten to sold the property to others..pse justify what can. I do to reclaim my gf property whole in my name...my father alive.