@MANOJ: Certainly there is a possibility though the outcome may be not certain as full facts are not known. But whether all this is possible without making the original owner/legal heirs as parties ? and the queriest has stated in the beginning that without involving the real owner/his legal heirs is the condition.. It is not clear as to whether the alleged seller and purchaser are related or not
My doubt is how specific performance suit without the knowledge of real owners/legal heirs? If there is an address (I am sure that queriest knows their address, but he wants to suppress this fact of his claim from them) the summons must be served to all legal heirs and expartee decree can be managed with good arguments and establishing consideration.
Again as the matter is more than 20 years, there should be some public record to satisfy the court if parties are not living now. . On learning of expartee suit decree, the real owner's legal heirs can still file declaration suit, after coming to know of such expartee decreed suit with his claims like not receiving summons etc.,
Without knowing facts and studying documents not prudent to offer straightforward guidance in view of so many complications. Better to remain calm and transfer the property through some gift or partition and thus creating a title deed and face further litigation as defendant in course of time.
(In similar case my friend as a legal heir of real owner is the victim. In his case the land was leased to a PSU for 40 years and his father was receiving lease rent. The dealer appointed by PSU has followed the procedure of filing specific performance suit, obtaining expartee decree suit and got property registered through Court. As real owner was receiving lease rent till the date of his death, he has not suspected foul play. Only when the dealer's family members partitioned the property after 44years it has come to his knowledge. In the meanwhile when the suit was filed, dealer disposed the property, and PSU handed over the property during Lis Pendens)