Giving Zakāh to one’s brother, or sister, or uncle, or aunt who are poor: Shaikh Ibn Bāz 

Shaikh Abdul-‘Azīz Ibn Bāz (rahimahullāh) said: “There is no harm in a man or woman giving their Zakāh to a blood brother or sister who are poor, or to their uncle or aunt – or to any of their poor relatives due to the generality of evidences.

Indeed giving Zakah to them is an act of charity and joining the ties of kinship due to the saying of the Prophet (ﷺ): “Charity to the poor is one act of charity whereas charity to a relative is an act of charity and joining a tie of kinship.” [1]

This giving of Zakah however does not apply to one’s parents and grandparents and their ascending line, nor to one’s children and grandchildren and their descending line. One cannot give their Zakah to this category of relatives even if they are poor. Rather it is obligatory for a person to provide for them from his wealth if he is able to do so, and there is no one else to spend upon them other than him.”

[1] Ahmad (15794) hadeeth of Salman Ibn ‘Aamir; An-Nasa’i (2582)

Source: http://www.binbaz.org.sa/fatawa/1541