Land deal done by using fake person to sign the registration papers

Hi, My Aunt has sold the land in 2001 to buyer1 and at that time out of 6 land co-owners(aunt+her sons/daughtersher husband's sister), one of the owner (Husband's sister) has never signed the papers and she did not about the deal, other 5 co-owners had signed the registration papers and for the 6th owner who never signed, they used other relative to sign it on behalf of her. Even documents of 6th owner (Aadhar card/Voter Id) in sale deed are fake persons documents. This is how buyer1 became the owner of that land. in 2009, same land is sold by buyer1 to buyer2, is there any way make that deal void and get the land back by original owners? Can you please guide me?