Why is everyone Duan Yu falls in love with, 'your sister!' ’？

Qiao Feng is loyal, benevolent, righteous, and filial, why does he say that he is disloyal, unrighteous, unkind, and unfilial in the end?

The Murong family has been restored for generations, and Murong Fu wanted to be the emperor, but finally fell to the top of madness?

……

What is the environment behind all these coincidences?

Born into Qin Hongmian's family 'Qinjiazhai', and Mu Wanqing learned martial arts together, the modern Qin Dynasty took you into the Northern Song Dynasty, and uncovered the secrets of Tianlong step by step.