Are the children of the owner's son entitled to claim a plot of land 17 years after their grandfather purchased it, based on the will of their father's insane grandfather to their father?

A grandfather's bequest to his non-inheriting grandson is enforceable if it is within one-third of the estate and the grandfather did not revoke it before his death. Its validity is not negated by its sale by a non-owner. Therefore, the children of the man for whom the land was bequeathed have a right to it if he was deprived of it due to his insanity. If they are awarded the land, the person from whom it was taken will have recourse against the seller for the price. The matter of entitlement is settled by referring to the Sharīʿah courts, as they investigate the validity of the bequest and the excuse for the legatee's silence. Entitlement is the annulment of one ownership by the establishment of another preceding it.