Is it permissible to give a portion of one's Zakat al-Mal to sisters to help them prepare their children for marriage?

It is permissible to give zakat to the poor children of sisters who cannot afford to marry except with money, and they have more right to it than others, according to the Prophet's (peace be upon him) saying: "Charity given to a poor person is charity, and charity given to a relative is two-fold: charity and maintaining kinship ties." The children must own the money first, and then use it to buy what they need for their marriage.