Can he give his zakaah to his married daughter who is poor as her husband is missing?
Question

                I have a daughter who is married and she has children, and her husband has been missing for a while. She has her own house. Can I give her my zakaah so that she can take care of the orphan children?.
Praise be to Allah.
    If a woman is married, then her maintenance is obligatory on 
    her husband. If he is poor or is absent and has not left her any money to 
    cover her maintenance, and she is poor and has no money, it is permissible 
    to her to be given zakaah. 

    Ibn Qudaamah (may Allaah have mercy on him) said in 
    al-Mughni (2/279): If a poor woman has a husband who is well off and 
    spends on her, it is not permissible to give zakaah to her, because she has 
    sufficient income from what she receives of obligatory maintenance. But if 
    he does not spend on her and it is not possible to make him do so, then it 
    is permissible to give zakaah to her. This was stated by Imam Ahmad. End 
    quote. 

    But her mother or father are not allowed to give her zakaah, 
    because he (the father) is obliged to spend on her in this case, except in 
    two situations: 

    1.Giving her zakaah in order to 
    pay off her debts which she borrowed for something other than maintenance.

    2.If the father is unable to 
    spend on her, but he has wealth on which zakaah is due, in which case it is 
    permissible for him to give her his zakaah.

    Shaykh Ibn ‘Uthaymeen (may Allaah have mercy on him) was 
    asked: is it permissible to give zakaah to a married daughter who is in 
    need? 

    He replied: in every case where a person meets the 
    description of those who are entitled to zakaah, the basic principle is that 
    it is permissible to give zakaah to him. Based on that, if a man is not able 
    to spend on his daughter and her children, he may give zakaah to her. But it 
    is better and more on the safe side to give it to her husband. End quote. 

    He was also asked: is it permissible to give my zakaah to my 
    married daughters, knowing that they are poor? 

    He replied: the scholars stated that a man should not give 
    zakaah to his offspring or to his father and grandfather or to his mother 
    and grandmother, in other words not to his ascendants or descendants. This 
    applies if it is given in order to meet their needs. But if they have debts 
    and it is not given as maintenance, then it is permissible to give it to 
    them, because he is not obliged to pay off their debts and hence giving his 
    zakaah to them is not regarded as a way to save money. 

    To sum up the answer: with regard to this man who has married 
    daughters whose husbands are poor, if he does not have sufficient wealth to 
    spend on them, then there is nothing wrong with giving his zakaah to them, 
    but he may give the money to the husbands, because they are the ones who are 
    responsible for maintenance. So there is nothing wrong with that whatever 
    the case. End quote. 

    Majmoo’ Fataawa Ibn ‘Uthaymeen (18/426) 
 And Allaah knows best.