Evonne was identified as the son of Liu E and Zhao Heng in The Song Dynasty Palace Ci. At the same time, Xiao Taihou proposed a truce with DaSong. If the two countries want to reach a peace agreement, they must send each other a prince as a hostage. Xiao Taihou arranged for Yelvkang to go to Dasong as a proton. Zhao Heng could not bear the pressure of courtiers and sent Evonne to Liao.
There is no Evonne in history, and Liu E and Zhao Heng have no children, because she can't have children. Obviously, Song Gong's poems were adapted on the basis of history.
Historical argument
Evonne in the Palace Ci in Song Dynasty is fictional. The real history is that Liu E never gave birth to a child, and Evonne was not among the sons of Song Zhenzong Zhao Heng. According to records, Song Zhenzong had five sons and two princesses, four of whom died young. Song Renzong Zhao is really the only surviving son of Zhao Heng. His biological mother is Li Chenfei, and his adoptive mothers are Liu E and Shu Fei. Zhao Zhen didn't know his life until Li Chenfei died.