Why is the surname Jiang instead of Xue? What is the relationship with Jiang and Jiang?

In the novel of TV series Hao Yixing, his biological father is not Xue, the god of life and death, but Jiang and Jiang, the head of the first medical school in the world.

It is said that his father Jiang is very capable, but he is mean, vicious, arrogant and aboveboard. Many female disciples in the clan secretly love him, but he can't accept the love between men and women normally. He is a patient with emotional acceptance disorder.

My mother, Wang, was once a female disciple on a lonely moonlit night. They followed the teacher's orders to double major together. In the process of double cultivation, Wang couldn't control his emotions, fell in love with Jiang, and even possessed himself, which made Jiang, who had emotional acceptance obstacles, unacceptable, thus making double cultivation impossible.

After Wang found out that he was pregnant, he resolutely left the lonely moonlit night and gave birth to a child. After learning the news, Xue, who had a crush on Wang for a long time, took NianLia to the top of life and death, regardless of the opposition of his elders, married Wang and picked up a bargain. Because Wang was in poor health, Xue didn't ask for his own children.

Then a hundred schools of thought contended and besieged the top of life and death. Before he died, Wang entrusted him to an orphan and told his life story, but in his heart, Xue was his only father.