Can Ragistered Relinquish deed made revoked after 19 months

In 2013 father prepared a will which was duly registered vide which he gave his own property y and his share in ancestral property in his son favor and all his cash ground 25 to 40 lacs with gold and silver ornaments distributed to his 2 daughters prior to preparation of his will and same was incororated in his registered will that from time to time he gave money to his daughters and all ornaments distributed to his daughters. Before preparation of will he did not discussed with his daughters nor The will was not disclosed to his daughters. Afterwards getting information about the will both daughters compelled father to cancel his will by preparing other fresh will without disclosing about receipt of cash and gold silver ornaments and sharing the father's own and ancestral property . Both parents were living with son only as he was taking care of parents. About change of will was not disclosed to son nor by father or his sisters. After the sad demise of father when son aproached his lawyer for change of name in municipal record and city survey office , on verification of previous will ,advocate told that it seems the will is changed. On enquiry son got the information the revised will is with younger daughter/ sister. He tried to discuss with his both sisters but we're adamant . After prolonged discussion with younger sister who was grabbed entire cash and gold ornaments then afterwards accepted about the same and relinquished her share in the property by registering the relinqish deed. Afterwards another sister also made relinquish deedwhich was registered. Now the younger sister want to revoke the relinquish deed thought her relinquish fees was made with her consent registered vegle two witnesses and by affixing her photography and singer behere the Registrar. There was no fraud, coiersion. In such circumstance whether she can revoke her registered relinquish deed after 19 months. The property has been already registered in sons name considering the death of father and relinquish deed registered by both sisters. In auch circumstances ahet her sister can record their registered relinqish fees. Pl confidence in that case what will be ramesh available to son .