Regarding ancestral property dispute between father and two sons

Res. Sir / Mam, I am sending this mail to get your legal opinion on a matter which involves my brother and me with my father. We are from a Traditional Agrarian Family who held huge land holdings in the Northern District of TN State. Our Family inherited lands from our forefathers through perpetual succession from kingdom days. My Grandfather had three Children (2 daughters & one Son {my Father}) they had mutual understanding among themselves and took a share on properties which they considered good for them. Our Properties consisted of a house at Chennai and an Ancestral House with 50 acres of land at the Village west of Chennai. One of the daughter of my grandfather ( aunt) took the house at Chennai considering it as her share from the properties and the other Aunt took 10 acres of land at Village by gift from my grandfather. My Father left with 40 acres of land and an Ancestral House at village started selling off those lands one by one thinking that my Aunts may ask for a share from that as well and eventually he exhausted all of them (as we thought) except the Ancestral house where we lived. All this happened when me and my brother were young (less than 10 years old) my mother wouldn't interfere in all these matters as she married my father out of her love for him. Now my Father who is 72 years old, have found a long lost piece of land ad-measuring 24 cents with Patta on his name, sold it off and fled the family by taking the money along with him. Now he is not living with us as a family, when we enquired about this sale, we came to know that he has given a power of attorney to sell to the buyer without any of our knowledge or signature and the buyer had paid him money the land is worth for. We have decided to challenge this and consulted our near and dear ones and they said you can file a suit but you need proof that the land is actually an inherited property so we applied for Encumbrance Certificate for 60 years all came as NIL as there was no transaction, because the land is with the family for 5 generations, even the land is on my father's name in the A-Register. An old Muncif suggested us to go to the Collector's office Records department where we can check for the settlement records of 1984 UDR, we applied for the same and are waiting for past one month with no response from them. We are struggling to establish that the Land is an inherited Ancestral property. Is there any way to Establish that my Father had inherited the aforesaid property from my Grandfather? In this due course we are being threatened both by my father and his siblings to not to interfere with the property matters and are disowning us as theirs; I am 27 years old and my brother is 24 years both of us majors, we never had any misunderstandings or dispute with our father, even though he exhausted properties worth fortune but he is all different now and have gone insane on everything. He has tarnished our reputation in the Village by spreading false statements of my mother and her past life and my birth. Please Suggest us a Legal way to tackle this situation as we are losing hope on finding a way to establish a link on the Property's inheritance With Millions of Thanks in Advance Regards, Prabhunath Vijesh.N