How can one advise elderly relatives and neighbors who do not pray, especially if they are illiterate and poor, and is mere advice sufficient to absolve oneself of responsibility towards them?

A Muslim should advise other Muslims, enjoin good, and forbid evil with wisdom. He should teach them matters of their religion, using admonition, encouragement, and deterrence. He should tirelessly supplicate for their guidance, especially if they are relatives or neighbors. If they respond, that is the objective. If they do not respond, and he has fulfilled his duty, then there is no blame on him. He should emulate the prophets whose peoples they called, yet only a few believed in them.