Fiqh-us-Sunnah Volume 3, Zakaat and Fasting, Fiqh 3.075.

Section : Fathers and Sons.

The jurists agree that it is not permissible to give zakah to one’s father, grandfather, mother, grandmother, son, grandson, daughter, and her children because the zakah payer is obligated to take care of all such people anyway. In case of their poverty, they should draw upon his largesse because it is their right. Thus, if he pays them zakah, he benefits himself and avoids the obligation of supporting them. Malik exempts the grandfather, grandmother, grandsons, and granddaughters because one does not have an obligation to support them if they are poor. However, if they are well-off and fought voluntarily for the cause of Allah, the zakah payer may give them some of the zakah designated for those fighting in the cause of Allah. He may also give them some of the share meant for debtors, though he is not obligated to pay off their debts. He may also give them a portion of the amount set aside for zakah collectors, provided they are in this category.