But the son heard that his father was ill, and his grandfather's family was destroyed by the state of Qin. He was afraid that the position of the monarch would be passed on to others and ran back to the state of Jin. Qin Mugong immediately decided to help Zhong Er become the monarch of the State of Jin and take over Zhong Er who fled to Chu.
I also married my daughter Huai Ying to him. In the second year, when Yiwu died, the son became the monarch of the State of Jin and had no contact with the State of Qin. With the help of Qin Mugong, Zhong Er became the new monarch of the State of Jin and Jin Wengong in the famous "Five Overlords in the Spring and Autumn Period".
Shortly after Zhong Er's death, Qin Mugong also took the opportunity to defeat the State of Jin, which had become the overlord of the Central Plains, and became one of the "five tyrants in the Spring and Autumn Period".
Therefore, the goodness of Qin and Jin represents a kind of political marriage and a union between countries. Later, the marriage between men and women was gradually called "the goodness of Qin and Jin".
Extended data:
Qin Jin friendship is a typical political marriage. The function of this kind of marriage is not to protect the happiness of individuals or families, but to realize political communication and political alliance (therefore, it is also called "Qin Jin's Horse", "Qin Jin's Union" or "Qin Jin's Covenant").
Monarchs after the Spring and Autumn Period were also good at promoting marriage and strengthening political alliances. In the Eastern Han Dynasty, Liu married a beautiful woman, Yin Lihua, and later married Liu Yang's niece, Guo Shengtong.
After Liu Xiu ascended the throne, he made Guo Shengtong the queen. After Liu Bei was conquered and Guo Shengtong was abolished, it can be seen that his marriage strategy was based on political considerations.
References:
Baidu Encyclopedia-Qin Jin's Good