Is the righteousness of the son a prerequisite for his prayer for his deceased father to be answered, or is the prayer accepted even if the son is not righteous?

Allah the Almighty commanded the child to supplicate for their parents, and He did not make the child's righteousness a condition for the acceptance of their supplication. The supplication of a child for their parents is among the rights of the parents after their death, whether the child is righteous or not. As for the Prophet’s (peace be upon him) restriction to "a righteous child" in the hadith about the cessation of a deceased person’s deeds except for three, it is for two reasons: that it is usually the righteous one who cares about supplicating for their parents, and that the supplication of the righteous is closer to acceptance. Some scholars have interpreted "righteous" as "Muslim." So, every Muslim is commanded to supplicate for their parents, and their supplication is hoped to be answered.