Is the questioner considered responsible for his siblings, and must he enjoin them to good and forbid them from evil, and must they obey him in that, or does the responsibility fall upon their mother, and what should he do if his mother falls short in that and leaves his siblings to commit some reprehensible acts?

Enjoining what is right and forbidding what is wrong is an obligation upon every Muslim at all times, and it is everyone's responsibility, as the Prophet said: "Whoever among you sees a wrong, let him change it with his hand; if he is unable, then with his tongue; if he is unable, then with his heart, and that is the weakest of faith."

This obligation is general for all Muslims and specific for fathers and mothers concerning their children. If the parents fall short, it becomes incumbent upon the son to exert effort in this matter with politeness and wisdom, as Allah Almighty says: "So fear Allah as much as you are able," and "Allah does not burden a soul beyond its capacity."

It is necessary to consider benefits and avert harms, and to show eagerness for their well-being and compassion towards them for their benefit, so that it may be more conducive to their acceptance.