How can one reform parents who do not pray and have not emerged from ignorance, despite the questioner's attempts to reform them?

The manifest loss on the Day of Resurrection is for a man to lose his family. Allah has commanded the believers to protect themselves and their families from the Hellfire. A man is a guardian and responsible for his flock. He must oversee his family by teaching, guiding, and admonishing them, being firm when necessary, and patient in inviting them to the truth. One should start with prayer, then abstain from major sins. Righteous companionship is beneficial in this regard. Do not despair or feel helpless; rather, be patient in enjoining good and forbidding evil, and increase in supplication and seeking forgiveness. Guidance is in the hand of Allah, and all a person has to do is strive and exert effort.