Is it permissible or impermissible for two sons to buy a minibus with a loan deducted from their father's pension, without giving anything to the rest of the children, and is the father obligated to give to the others?

Parents must be just among their children in giving gifts, based on the Prophet's (peace be upon him) saying: "Fear Allah, and be just among your children." So, whoever singles out some of them with a gift has sinned, and it becomes obligatory for him to equalize, unless there is a reason that necessitates favoritism, such as need, poverty, inability to work, debt, and the like. In such cases, there is no harm in singling out the needy person over others. If the loan was usurious, then repentance from this grave sin is obligatory.