Shaykh Abdul Azeez ibn Baaz rahimahullaah was asked in his Majmoo` Fataawaa vol. 14, page 301:
Q: Is it permissible for a person to pay zakat (obligatory charity) to his own brother who is in need (he has a large family & works but his income does not suffice him)? Likewise, is it allowed (to be paid to) the paternal uncle who is poor? Also, can the woman pay zakat (obligatory charity) from her wealth to her brother, or her paternal aunt, or her sister?
A: There is no problem in a man or a woman give their zakat (obligatory charity money) to their poor brother, or a poor sister of theirs, or a poor paternal uncle of theirs, or a poor paternal aunt of theirs, and likewise the rest of their poor relatives; due to the generality of the evidences.
Rather giving zakat (obligatory charity money) to them is a charity and a joining of the ties of kinship, due to the saying of the Prophet sallAllaahu `alaihi wa sallam: “Giving charity to a poor person is charity, and (giving charity) to a relative is charity and upholding the ties of kinship.”
[Reported by Ahmad no. 15794, an-Nasaaee no. 2582, and Ibn Maajah no. 1844, and graded as ‘Saheeh’ authentic by Imaam al-Albaanee rahimahullaah]
Except for ones parents, and those above them (i.e. grandparents, great grandparents ect), or ones male or female children, and those below them (i.e. grandchildren, great grandchildren ect), then it (zakat) is not to be paid to them, even if they were poor.
Rather it is binding upon him that he spends upon them from his wealth if he is able to do so, and (if) there is nobody else that will spend upon them other than him.