Am I permitted to refrain from sending a monetary gift to my parents if they spend it on my siblings who are not in need?

If parents are not in need of money and give gifts to their children who are also not in need, then it is not obligatory to give them gifts. However, it is advisable to strive to please them and to offer gifts that do not harm the giver, especially if withholding gifts would anger them; for honoring parents is among the greatest acts of piety.