No, a gift, once accepted, cannot be given back unless the gift giver accepts it back voluntarily--she cannot be forced to take it back. And since the grandmother has passed, she cannot accept it back. Your son and his wife can most likely let the home be foreclosed upon without it affecting their credit, since they were not (presumably) parties to or signatories of the mortgage: that is, while the bank has the right to demand that the loan be paid in full when the borrower passes or they will foreclose, your son and his wife did not necessarily become liable for the loan, unless they signed something taking responsibility for it. If so, they should be able to let the bank foreclose and simply walk away from the home.