Liu Feng was a descendant of the Marquis of Luo (), whose family name was Kou (). He was also related (but not directly) to the Liu () family of Changsha (長沙; around present-day Changsha, Hunan), who descended from Liu Fa (), one of Emperor Jing's sons. When Liu Bei seized control of four commanderies – Changsha, Lingling (), Guiyang (), Wuling () – in southern Jing Province (covering present-day Hubei and Hunan) in 209, he adopted Liu Feng as his son because he had no suitable heir at the time. In 211, Liu Bei led an army from Jing Province to Yi Province (covering present-day Sichuan and Chongqing), ostensibly to help Yi Province's governor Liu Zhang counter a rival warlord Zhang Lu in Hanzhong Commandery. When war broke out between Liu Bei and Liu Zhang in the following year, Liu Feng, then in his early 20s and famous for his combat skills and great physical strength, led forces from Jing Province together with Liu Bei's other followers to assist his foster father in the Yi Province campaign. Liu Zhang surrendered to Liu Bei in 214, after which Yi Province came under Liu Bei's control. Liu Bei appointed Liu Feng as a Vice-General of the Household ().