Is a brother obliged to spend on his sister?
Question

                Is a brother obliged to spend on his sister? Is it permissible for her to take zakaah from her brother’s wealth?.
Praise be to Allah.
    A brother is obliged to spend on his sister if she is poor 
    and he is independent of means and he would inherit from her if she died. If 
    he would not inherit from her because she has a son or because the father or 
    grandfather (father's father) is still alive, then he is not obliged to 
    spend on her and it is permissible to give her the zakaah of his wealth in 
    that case. 

    Ibn Qudaamah (may Allaah have mercy on him) said in 
    al-Mughni (8/169):  

    In order for maintenance to be obligatory, three conditions 
    must be met:

    (i)They should be poor and have no 
    wealth or source of income which would make them independent of being 
    maintained by others. If they have enough wealth or income to make them 
    independent of means, then it is not obligatory to spend on their 
    maintenance.

    (ii)The one who is obliged to spend 
    on their maintenance should have enough to do so, surplus to the costs of 
    his own maintenance, either from his wealth or his income. If he does not 
    have any surplus, then he is not obliged to do anything, because of the 
    report of Jaabir that the Messenger of Allaah (blessings and peace of Allaah 
    be upon him) said: “If one of you is poor, then let him start with himself. 
    If he has any surplus, then let him spend on his dependents, and if he has 
    any surplus, let him spend on his relatives.”

    (iii)The one who spends should be an 
    heir, because Allaah says (interpretation of the meaning): “And on the 
    (father’s) heir is incumbent the like of that (which was incumbent on the 
    father)” [al-Baqarah 2:233]. And because there are ties of kinship between 
    those who would inherit from one another which dictate that the heir is more 
    entitled to the wealth of the one who leaves it behind than anyone else, so 
    by virtue of the ties of kinship he is to be singled out for maintenance 
    rather than anyone else. If he is not an heir, then he is not obliged to 
    spend on his maintenance. End quote.

    Shaykh Ibn ‘Uthaymeen said in al-Sharh al-Mumti’ 
    (13/503): 

    The basic principle in our view is that it is essential that 
    the one who spends be an heir of the one on whom he spends, except for 
    direct ascendants and descendants, in which case the issue of inheritance is 
    not a condition. End quote. 

    Based on this, if the brother is obliged to spend on his 
    sister, it is not permissible to give the zakaah of his wealth to her, but 
    if he is not obliged to spend on her, it is permissible to give the zakaah 
    of his wealth to her, and indeed that is better than giving it to someone 
    else who is not one of his relatives, because by doing this he will attain 
    the reward of both zakaah and upholding the ties of kinship. 

    And Allaah knows best.