The ruling on a father spending on his poor son to the exclusion of the wealthy one

Question:
A message was received by the program from the Arab Republic of Egypt, Minya Governorate, and the sender of the message is the listener Khaled Talaat Abdullah Ali. Brother Khaled says in his message: A man has two married sons, and each of them supports a family. One of these two sons is in a comfortable financial situation, while the other has many expenses and needs some assistance. So the father allocated a fixed income to this needy son at the father's own wish, and without any request from this son. However, the other son rebelled against his father and his brother, and considered that his father was favoring his brother over him.
The question is: Is this permissible in the Shari'ah? It is known that the son benefits from his father's gift to him only during his lifetime.
May Allah reward you with good.

Answer:
If one of the two sons is poor and does not have the means to support himself, then the father must spend on him if he is able to do so, and the wealthy son has no right to that. So if a man has children, some of whom are poor and some are wealthy, and the father is able to provide for them, it is obligatory for him to spend on the poor ones, even if they are adults, provided they do not have means that make them self-sufficient, and no earnings that make them self-sufficient; because providing for one's children is a necessary duty for the father to spend on his poor son.
As for if they are all wealthy, then he is not allowed to give a gift to one of them exclusively; because of the saying of the Prophet (peace and blessings be upon him): So it is obligatory that he be just if they are poor, by spending on them and being just among them, and if they are wealthy, he should be just among them as well, by giving to all of them, or leaving all of them. As for if one of them is poor and the rest are wealthy, or most of them are poor and some are wealthy, then he spends on the poor one, and this is not injustice, but rather it is obligatory for him to spend if the poor one does not have means, does not have earnings, and is unable to earn. So if the father is able to do so, he spends on him and helps him with the expenses of his peers. Yes.

The presenter: May Allah reward you with good.