Although Liu Fei is the eldest son of Liu Bang, he is the son of Liu Bang, and he had an affair with the widow Cao Shi before he became rich. His pedigree has been criticized, but Liu Bang didn't care, because he knew that Liu Fei was his own son, so Liu Bang raised Liu Fei the richest after he proclaimed himself emperor. He gave not only the richest land in Liu Fei, but also the cities with the most sons. Because Liu Fei is the eldest son of Liu Bang, he is still a member of the Liu family.
After Liu Bang's death, Lv Hou came to power, and those concubines who once made Lv Hou's teeth itch were retaliated by Lv Hou. Lv Hou not only retaliated against Liu Bang's concubines, but also persecuted Liu Bang's son, mainly for fear that Liu Bang's son would shake her son Liu Ying's throne, so Liu Bang's son was either killed by her or forced to commit suicide or starve to death.
Liu Fei must have been very scared. His counselor told Liu Fei that Lv Hou had always loved his children, and Liu Ying was already an emperor, so there was nothing to lose. However, Lv Hou's daughter Princess Lu Yuan did not have many fiefs. If Liu Fei can dedicate her city to her sister Lu Yuan, then Empress Lu will be very happy and won't be angry with him. Liu Fei has a point, but he doesn't think it's enough, so he has the cheek to admit that his sister is his godmother.