Am I obligated to tutor my brother at university based on my father's request, and would I be sinful if I refused to do so?

"University expenses are not included in the obligatory maintenance (nafaqa) for the father or the brother. However, obedience to the father concerning this expense, if the son is capable, is considered a great act of goodness due to it encompassing obedience to parents and maintaining kinship ties. Therefore, it is advised to try to obey the father as much as possible, as long as it does not harm the son."