Assumption:
The seller is a Hindu. The deceased owner died intestate. There are no daughters.
The property's character whether of a joint Hindu family,or self-acquired, is not clear. Assumed as self-acquired.
Oral partition is valid under Hindu law. Does not need registration. Also agreement of sale does not need registration. However the agreement should have been adequately stamped as per local stamp act, lest penalty shall entail.
The agreement in question, is stated to have been executed by the same person who had relinquished his rights under oral partition.How and when this knowledge of relinquishment came to thre knowledge of the intending purchaser is a relevant factor in evidence.
Action suggested:
1.Issue notice to RST, the person holding out as 'owner' under the agreement, for specific performance alongwith co-owners if any, and furnishing the necessary collateral documents like power of attorney from the co-owners, if any or patta/khata transfer, latest tax paid return and receipt. Notice may mention alternative remedy of refund with penalty/interest, as per the penalty clause if any in the agreement.
2. Knowledge of existence of co-owners or defect in the title of the noticee (which obviously have come to light after the agreement is executed) may be mentioned in the notice, depending on the circumstances.
3. When no reply/inadequate/unsatisfactory reply is received within the period mentioned in the notice, file suit under specific relief act, with alternative remedies or money-recovery remedy only, depending upon the purchaser's wish as well as capacity to stake the court fee.
4.If arbitration clause is there in the agreement, after the notice period, approach the proper court, under section 9 of the A & C Act, for interim relief of stay on alienation or creation of third party interests on the property;
5.After filing Section 9 application,take steps to refer the dis[pute to the named arbitrator if any or initiate Section 11(6) proceedings in High Court, for appointment of an arbitrator.