Is the graduate obligated to return the refunded amount from the university to his father who paid the fees, or is it permissible for him to keep it in exchange for his personal expenses which his father also used to cover?

University tuition fees are not part of the obligatory expenses a father must provide for his children. If the money given by the university to the student is a reward for him, then it is his property, and he is not obligated to give it to his father. However, if the university refunds a portion of the tuition fees that the father paid, then, in principle, it is the father's right, unless he willingly relinquishes it to the student.