What is the relationship between fetal qi and desire?

According to the inquiry of Mile Mile app, it is known that fetal spirit and desire for love are father-son relationship. "God Bless the People" tells the story of Yue Xian Prince Xie Lian who failed to climb the mountain twice in a row, and Yue Xian divined that his ascent would be a catastrophe. In order to avoid Xie Lian's pain, Buddhism reduced him to a mortal. After Xie Lian climbed the mountain for the third time, he met the mysterious Wang Huacheng in the mortal world, and they traveled the rivers and lakes together.