1. Yes, once a joint principal of a PoA dies, the PoA stands revoked in law.

2. No, it doesn't matter if one of the joint principals is a legal heir or not.

3. The three-year limitation starts from the date of discovery of fraud.

POA ceases on death of the principal (A)

2) land was owned by A only not by his legal heirs .it does not change any thing 

3) fraudulent sale was discovered now and suit has been filed within period of 3 years .claim is not barred by limitation 

1. If the GPA is not clubbed with interest then it automatically stands revoked/cancelled upon the death of the Principal, hence the sale deed executed subsequent to the death of the Principal by the power agent is invalid and illegal.

2. Even if one of the Principals is died, the GPA deed stands automatically cancelled 

3. The limitation to challenge the sale deed is three years from the date of knowledge.

Sir/Madam, 
It is suggested that the GPA might be containign all the relevant clauses, regarding its termination, including after the death of perosn_A. if this clause is not given in GPA, then wife and children must have taken taken appropriate steps to revoke the GPA after the death of Person_A. Undoubtedly, those who would become Person_A's heirs (wife and children) are also on the GPA change anything. It is material fact to note that when the sale of the land has come to the notice of wife and children of the person_A. if the same is in limitation, their objections will be valid. 

1. The GPA gets nullified upon the death of the Principal, in the instant case it's upon the death of person_A. 

2. However,  if the Principal had received money for executing the GPA, then the GPA wouldn't lapse after the death of the Principal.  The Principal's legal heirs have to honour it.

3. Twelve years is the limitation period to contest /challenge the GPA for title recovery of the property.  However it's upto the Court to condone delay in filing the petition.  

Based on the facts stated by you, the answer depends upon the precise nature of the GPA, the authority granted under it, whether it was coupled with any interest, and the capacity in which the wife and children executed the document.

As a general rule under the law of agency, a Power of Attorney is terminated upon the death of the principal. Therefore, if Person_A alone was the owner of the property and granted a GPA to Person_B, the authority of Person_B would ordinarily come to an end upon Person_A's death. In such a situation, any sale executed by Person_B after the death of Person_A would generally be vulnerable to challenge because an agent cannot act on behalf of a deceased principal.

However, your facts introduce an important complication. You state that not only Person_A but also his wife and children executed the GPA. If the wife and children signed the GPA merely as consenting witnesses or confirming parties, the position may not change significantly. On the other hand, if they executed the GPA as independent principals conferring authority upon Person_B, then the GPA may continue to remain effective to the extent of the rights and interests of those surviving executants. The exact wording of the GPA becomes critical.

Another important question is whether the property belonged exclusively to Person_A or whether the wife and children already possessed a present legal interest in the property when the GPA was executed. If the property was exclusively owned by Person_A, the wife and children generally would not have acquired ownership merely by signing the GPA. Their rights would ordinarily arise only upon Person_A's death through succession.

As regards the sale made by Person_B to Person_C, if the sale deed was executed after Person_A's death and solely on the basis of authority derived from Person_A, the sale may be challengeable. However, if the surviving executants validly authorized the transaction and had acquired interests in the property upon Person_A's death, the analysis may be different.

Coming to your third question, a challenge raised after approximately twenty years faces serious limitation issues. Under the Limitation Act, suits for cancellation of instruments, declaration of title, or challenges to registered conveyances are generally required to be brought within prescribed limitation periods, often calculated from the date when the plaintiff first became aware of the transaction. Courts are generally reluctant to unsettle long-standing registered transactions after decades, particularly where the purchaser has remained in possession, revenue records have been mutated, third-party rights have intervened, and the challenge is highly delayed.

Further, principles such as limitation, acquiescence, waiver, estoppel, laches, and adverse possession may become relevant depending upon the facts. Therefore, even if there was an initial defect in the authority of the GPA holder, a challenge after twenty years may face substantial procedural and equitable hurdles.

In my view, the most important document to examine is the GPA itself. The answer will largely depend on:

1. Whether the wife and children executed it as principals or merely as consenting parties.

2. Whether the GPA was revocable or coupled with an interest.

3. Whether the property exclusively belonged to Person_A.

4. Whether the sale deed recites that Person_B was acting on behalf of all executants or only on behalf of Person_A.

5. What happened in the twenty years following the sale, including possession, mutation, and enjoyment of the property.

Without examining those documents, it would be difficult to conclude that the sale is automatically void merely because Person_A had died before execution of the sale deed. However, as a general proposition, a GPA granted solely by a principal ordinarily ceases upon that principal's death.