1) apply for and obtain legal heir certificate of your grand morher ,father,mother
2) you must have death certificate of your grand mother ,father ,mother
3)The 1976 war-widow/dependent military incentive allotment order is your strongest evidence. Ensure it is preserved, as government land granted to defense personnel who died in war carries strict non-alienation violations if occupied by unauthorized third parties.
4)File a formal Title Appeal under Section 5(5) of the Andhra Pradesh Rights in Land and Land Revenue Act (ROR Act) before the Revenue Divisional Officer (RDO) of your division.
5)take the plea that Pattas obtained are fraudulent as land allotted to military personnel cannot be assigned to third parties
6) enclose military incentive allotment order ,death certificates and legal heir certificate and representation made to tehsildar