Can he give his zakaah to his brother on whom his father spends?
Question

                Is it permissible to give my zakaah to my brother who has not yet completed his university studies because of psychological problems and has not found a job? He is currently staying with my father who spends on him. Please note that my father is not very well off.
Praise be to Allah.
      Giving zakaah to one's deserving relatives is better than 
      giving it to those who are not your relatives, because charity given to a 
      relative is both charity and upholding the ties of kinship. But if these 
      relatives are among those on whom you are obliged to spend, then it is not 
      permissible for you to give your zakaah to them. 

    See the answer to question no.
    20278 

    Spending on your brother is obligatory for your father, but 
    if your father is not able to spend on him, it is permissible for you to 
    give your zakaah to him.  

    The scholars of the Standing Committee were asked: 

    My father died (may Allaah have mercy on him), and left 
    behind a family of seven people, including another wife besides my mother. 
    They do not have any source of support apart from Allaah. Is it permissible 
    to regard what I spend on them of my own money as zakaah, knowing that I am 
    married and support another family of my own? 

    Secondly: I have an older brother who is married and has two 
    wives, and he has a lot of children and can hardly afford to look after 
    them. He often asks me for help. Is it permissible to regard what I send to 
    him as zakaah? 

    They replied: 

    There is no reason why you should not send zakaah to your 
    siblings through your father, both males and females, in the future, if they 
    are poor and do not have sufficient wealth to render them in no need of 
    zakaah. Similarly it is permissible for you to send zakaah in the future to 
    your older brother if he is poor and has no wealth or earnings to render him 
    in no need of zakaah, because of the general meaning of the verse on zakaah, 
    in which Allaah says (interpretation of the meaning): 
“As-Sadaqaat (here it 
    means Zakaah) are only for the Fuqaraa’ (poor), and Al‑Masaakeen (the poor) 
    and those employed to collect (the funds); and to attract the hearts of 
    those who have been inclined (towards Islam); and to free the captives; and 
    for those in debt; and for Allaah’s Cause (i.e. for Mujaahidoon — those 
    fighting in a holy battle), and for the wayfarer (a traveller who is cut off 
    from everything); a duty imposed by Allaah. And Allaah is All-Knower, 
    All-Wise”

    [al-Tawbah 9:60]

    Shaykh ‘Abd al-‘Azeez ibn Baaz, Shaykh ‘Abd al-Razzaaq 
    ‘Afeefi, Shaykh ‘Abd-Allaah ibn Ghadyaan. 

    Fataawa al-Lajnah al-Daa’imah, 
    10/57, 58. 

    Elsewhere they said: 
It is permissible for 
    you to give to your half siblings and wife’s father zakaah that will suffice 
    them, if their income is not sufficient for them. 

    Fataawa al-Lajnah al-Daa’imah, 
    10/59 

    Shaykh Muhamamd al-Saalih al-‘Uthaymeen (may Allaah have 
    mercy on him) said: 
With regard to your 
    question as to whether it is permissible to give zakaah to a half-brother or 
    full sister, the answer is that if giving zakaah to them  involves waiving 
    something that is a duty for you, such as if it is obligatory for you to 
    spend on them, and you give them zakaah so that you will not have to spend 
    on them and can save money, that is not permissible, because zakaah cannot 
    be a means to avoid spending. But if it does not, such as if you are not 
    obliged to spend on a person, because you are not one of his heirs, or 
    because you cannot afford to spend on him as well as your own family, or you 
    give it to him to pay off a debt that he owes and cannot repay, then it is 
    permissible for you to give your zakaah to him, and indeed that is better 
    than giving it to someone else, because giving it is both charity and 
    upholding the ties of kinship. 

    Majmoo’ Fataawa Ibn ‘Uthaymeen, 
    18/422, 423. 

    See also the answers to questions no.
    21810 and
    11492 

    And Allaah knows best.