Whose son is Duan Yu?

Duan Yu, one of the leading men in Jin Yong's martial arts novel Tian Ba Long Bu, is the prince of Nanwang section of Dali Kingdom (actually born with Dao Baifeng).

Duan Yanqing, the prince of Dali, was persecuted by treacherous court officials and escaped from the palace. Later, surrounded by strong hatred, it was beyond recognition. His legs are disabled and he can only communicate in abdominal language. I wanted to die, but I regained my faith because of my dew love with Dao Baifeng. After recovering from his injury, he took revenge on those who killed him that year. Because of the cruel means, he won the title of "the head of all evils" and became the head of the "four wicked people".