Ancestral Property Dispute- Proper Partition Issue

Our ancestor property (currently it's under gram panchayat) is in the name of our Great Grandfather, who had 3 sons (all expired now, among 3 one is my grandfather ), and since 1963 tax has not been paid. Ideally, there must be 3 partitions of the piece of land but they are not ready for 3 divisions as one of the grandfather's sons has taken 40%-50% of the land and constructed a house. And now my father and other 2 cousins wanted to separate the property, how it will be the partition and how I can go ahead and separate the ownership of land in my father's or in my name, if possible. My parents and I don't live there for 3-4 years so it has become very troublesome for us, now am interested in selling off that property but my father's cousins are saying you cannot sell off this until the partition also on the other side they are not ready also for the 3 partitions of the land and not giving us NOC and signature for the partition legal procedure. ​