What should I do about my brother who used to be regular in prayer and fasting, but then turned around to disrespect his father, smoke, listen to music, abandon prayer, and his sins and problems increased, despite attempts to reform him through beating and preventing him from going out?

The method of violence and harshness only exacerbates the situation. Therefore, it is advisable to use gentleness, leniency, and counsel in the best manner, such as gifting some tapes and booklets that address the areas of deficiency, and endeavoring to create a righteous environment and good companions who assist in obedience to Allah, knowing that guidance is in the hand of Allah. One must take the necessary means, for Allah Almighty says: "Indeed, you do not guide whom you like, but Allah guides whom He wills."