100 year old man and 200 year old man

The emperor and his entourage suddenly stopped on the road and the Emperor demmanded to know the meaning of it. He found that a young man was beating an old man. He had them both brought before him and asked of the young man, "Young man! Why are you beating this old man!"The young man, or so he looked to be, said,"Young man? I am over two hundred years old. This fool is my son. He is only one hundred. Why can't I beat him?"A crowd had gathered. After some research the Emperor found this to be true."How is it that you appear young while your son appears old?" asked the Emperor."I appear young because I practice Mein Lay Jum. I beat my son because though he knows Mein Lay Jum he does not practice, and so has come to appear older than me." said the two hundred year old man.The Emperor took both of them and had the two hundred year old man teach the Imperial Guards this powerful Kung Fu.