Why is Qi Heng called Xiao Gongye?

In Know If You Should Be Green, Fat, Red and Thin, Qi Heng is called "Xiaoyegong" to show his respect because his father is Qi Huangong.

Qi Heng is the son of the Duke of Qi, and his mother's is also a princess, so the family status is very noble and others respect them. In ancient times, lord protector was a title and was regarded as the highest-ranking official except the royal family. Just as the duke's son is called the little duke, the little duke is also a courtesy title for outsiders to be the heir to the Lord protector.

In Know No, Qi Heng spent some time in Shengjia private school. The daughters of the Sheng family, such as Lan and Moran, are both called Qi Hengyuan's brother, and only Sheng Minglan calls him Xiaoyegong. This kind of address has a polite alienation, which makes Qi Heng pay some attention to her. Ming Lan, of course, called it just to keep his distance, not to attract him.

However, although Qi Heng is a powerful person, his status has advantages and disadvantages. The status of the duke of Qi brought him supreme glory and endless wealth, but deprived him of the right to choose love.