Ruling on giving zakaah to a daughter through breast-feeding
Question

                Is it permissible for a man to give zakaah to his daughter through breastfeeding, if she is poor?.
Praise be to Allah.
      If the man has children who are poor, it is not permissible 
      for him to give the zakaah of his wealth to them, because it is obligatory 
      for him, according to sharee‘ah, to spend on them and make them 
      independent so that they do not have to ask others for what they need. 
      There are some exceptions to this ruling; for more information see the 
      answer to question no. 105789 
      and 130207. 

    This applies to one’s own children and grandchildren. With 
    regard to children through breastfeeding, it is permissible to give them 
    zakaah, because one is not obliged to spend on them. 

    Ibn Qudaamah (may Allah have mercy on him) said: The scholars 
    of the ummah are unanimously agreed that relatives through breastfeeding are 
    mahrams. With regard to the other rulings connected to kinship through 
    blood, such as spending on maintenance, manumission, rejecting testimony and 
    so on, they have nothing to do with the relationship through breastfeeding, 
    because blood ties are stronger than it, so an analogy cannot be drawn in 
    all rulings; rather the resemblance is only in the matters referred to by 
    the shar‘i text. End quote  from al-Mughni. 

    He also said (8/169): All of the scholars from whom we 
    learned are unanimously agreed that a person is obliged to spend on those of 
    his children who have no wealth. With regard to spending being obligatory, 
    three conditions must apply… the third of which is that the one who spends 
    should be an heir. End quote. 

    Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) said:

    Breastfeeding does not make any of the rulings to do with 
    kinship applicable except those that have to do with marriage only; 
    breastfeeding creates the relationship of mahram, makes it permissible to 
    look (at the person) and haraam to marry that person. But it does not make 
    the people concerned heirs of one another or mean that one is obliged to 
    spend on the other or to pay the costs of diyah or to uphold the ties of 
    kinship, as in the case of blood relatives. Most of the rulings of blood 
    ties do not apply in the case of breastfeeding. End quote from Noor ‘ala 
    al-Darb. This has also been explained in detail in the answer to 
    question no 40005. 

    Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) was 
    asked: 

    Can zakaah be given to one’s mother through breastfeeding and 
    sister through breastfeeding? 

    He replied: Yes, zakaah may be given to one’s mother through 
    breastfeeding and sister through breastfeeding, if they are entitled to 
    zakaah. That is because one is not obliged to spend on the mother through 
    breastfeeding and the sister through breastfeeding; so zakaah may be given 
    to them on condition that it be proven that they are entitled to it. End 
    quote from Majmoo‘ al-Fataawa, 18/417 

    And Allah knows best.