Is it permissible for a son to pay the Zakat on his father's money from his own money and give it to his needy, married brother who lives alone?

It is permissible to give zakat (definition) to a brother if his sustenance is not obligatory upon the zakat-payer and if he is eligible to receive zakat. This is better as it combines charity and kinship, according to the hadith (definition): "Charity given to a poor person is one charity, but given to a relative, it is two: charity and strengthening of kinship." However, if his sustenance is obligatory upon the zakat-payer, or if he is not eligible to receive zakat, then it is not permissible to give him from it.