Is the grandmother's verbal relinquishment of her right to inherit from her two deceased sons nullified and returned on the grounds that it is a gift and a gift can be revoked, especially since she did not claim it for six years?

A grandmother's relinquishing of her share to her grandchildren is considered a gift, and it is valid if she is not interdicted and the donees take possession of the gift during her lifetime. If they do not take possession, the gift is not complete, and her share becomes an inheritance to be divided according to Sharia (definition). However, if she relinquishes it during her death illness, it is considered a will that is executed within the limits of one-third of her estate, and anything beyond that depends on the consent of the heirs.