What is the ruling on one who, in the past, ignorantly committed acts of the people of innovation, such as beating the chest and wailing in funeral processions? And does the ruling differ if the person's relatives did so out of ignorance and then came to know the ruling?

Your relatives' father was correct in preventing them from innovations, and we hope Allah accepts their repentance. They may be excused due to their ignorance. We advise them to learn the rulings of the Sharia, to increase in righteous deeds, and to be keen on getting to know the people of Sunnah and uprightness. The relatives who are adhering to innovations should be advised and guided to adhere to the Sunnah.