Is it permissible for a man to give zakat to his father's wife and his siblings (full siblings or paternal half-siblings only) if his father is stingy and they live with him in one house but are separate in food and drink?

It is not permissible to give zakat (definition) to a poor father, because his maintenance is obligatory upon his son. As for the father's wife and children, their maintenance is the responsibility of the able father. However, if he does not provide for them due to his stinginess or poverty, it is permissible to give them zakat, provided that the father's wife is not his only wife. If she is his only wife, and the father is poor and the son is wealthy, then her maintenance is obligatory upon the son. Likewise, it is not permissible to give zakat to the mother, even if she is a second or third wife to the father.