Settlement Land

Sir, I had purchased a land from a family which they got allotment in the year 1957,but after few years i came to know that the land which i bought was not allotted to them(Seller) ,instead it was allotted to their cousin brother's father. Now they are coming up with some piece of document, which as i have said ,that it was allotted to them on 1957 between two brothers, Plot 5 and 7 was allotted to both brothers. As i have bought plot 5 from a person(seller) which they sold me stating that the owner of plot 7 doesn't exist and all their family members have passed away and they are the one in possession of Plot No. 7. But now after 10 years of my possession upon land the people from the other family came up who have not passed away but still exist came up with the allotment letter which they got in 1957. But as per land records the land category is Govt. Land and after applying for Settlement our district administration has offered me that i can pay the revenue and can get the settlement by paying a premium amount but i need a possession period of 20 yrs and above. Sir, my question is can the party still will have a possession as the land is govt land as per the record also party have a settlement document from govt. from the year 1957 but they dont have any other documents and also they don"t even have a possession.