Is it permissible to give zakat to an unemployed father who has no income but is supported by others, and to a grandmother who does not live with the zakat-payer and has no income?

It is not permissible to give zakat to parents or grandparents if they are poor, because their financial support is obligatory upon the zakat payer. Giving them zakat would relieve him of this obligation, and the benefit would return to him, making it as if he paid zakat to himself. However, it is permissible for the zakat payer to give zakat to his indebted father, because a debtor is one of the categories eligible for zakat, and he is not legally obligated to pay off his debt.