Is it permissible for a mother to pay Zakat al-Mal on behalf of her son, who is married to two women and is not financially capable, in Palestine?

Zakat is only obligatory upon one who possesses the nisab (minimum threshold) of 85 grams of gold and upon which a full year has passed. If the son does not possess that, then zakat is not obligatory upon him, and the mother is not required to pay it on his behalf. As for Zakat al-Fitr, it is obligatory upon every Muslim who possesses sustenance for the day and night of Eid, and the mother can pay it on behalf of her son and his family.