Is it permissible to count university installments paid for a poor brother as being from zakat funds?

The fundamental principle is that a child is considered rich by virtue of his father's wealth, due to the obligation of the father to spend on him. Educational expenses are among these obligatory expenditures. However, if the father is unable to spend on his impoverished child, it is permissible to give him Zakat to cover university tuition fees, even if the one spending on him is doing so voluntarily, because the obligatory expenditure on the father is waived due to his inability.