Legal opinion on inherited property

If it was an ancestral property, the children of A also have coparcenery rights by birth in the property, suppose the property was sold by A during the minority of his children without obtaining permission from court of law and that too sold the property on his own not mentioning that he is selling the same on behalf of his minor children for their educational or future benefits as their natural guardian, the said sale can be considered as invalid.  As you say that its around 17 years of time that has passed after the said sale and since A's son himself has signed as a witness, proceed with the purchase.