Since the Inam land is allotted for occupancy or ten ency rights only, the inamdar cannot alienate the proeprty by sale without the permission of the Commissioner of the land revenue.
If this violated then the sale be rendered as invalid if it is brought to the notice of the competent authority/revenue department
Under the Ryotwari System every registered holder of land is recognised as its proprietor, and pays direct to Government.
Section 11 of Andhra Tenancy Act: where a person is in occupation of inam land is prima facie entitled to ryotwari patta as per section 4 of the act.
If the ryotwari patta has been granted to the ryot then he becomes the owner of the landed property with clear title to his name, however he may have to abide by the conditions imposed while granting the inam land to him as a ryot, for proceeding with the alienation.
If the conditions were violated then the sale of land to a third person may be rendered as invalid.
You may confirm that if they have filed the suit invoking section 4 of the HSA .
Whatever, you may have to challenge the same on merits and documentary evidences in your support.