My grand parents property transferred to foster son where there are 7 born daughters to them

My grand father had 2 wife's 1st wife has 6 female children and 2nd wife has 1 female children and no male issue to them. My grand father passed in 1964. In 1967 my grand mothers bought a male child from nearby village to look after the house hold activities later he shined him self on the surname of my grand parents but they is no adoption of that male child (foster son only). On 17/10/1997 that male child passed away leaving his wife and 2 male child's and 1 female child. On 19/10/1997 my 1st grand mother passed away and 2nd grandmother passed in 1995 only. They did not leave any will during their life time so all the properties remained undivided till date. But we were shocked to see that the names in the revenu records were changed from my grandmother name to the name of the deceased foster son wife. None of their 7 daughters gave noc for the transfer of the same. While we applied for the information under RTI act the MRO office personals says that their is no legal heir certificate, dearth certificate, tax certificate, pattadar passbook details, noc from the born children. But they transferd the name of the owner from my grandmother to the name of the deceased foster son wife. Kindly suggest me us to get the issue settled legally.