There is an old Kung Fu movie where a mother trained her two sons to beat an old Kung Fu Master. The father was killed by the master. The mother trained her two sons on her own. I remember in particular how the mother trained one of the boys to be invincible. She scolded his entire body in a tub of hot water and had the brother use a whip on him immediately afterwards. Most of the movie was the two training and getting stronger. The ended up defeating the Master in the end. I cannot remember the name of this movie. It was as good as The Executioners of Shaolin.
This movies was back in the 70s. It was one of the Saturday morning Kung Fu movies.