Sima Yi's ancestral home was in Xiaojing (), Wen County, Henei Commandery. His ancestor was Sima Ang, the King of Yin (), who was briefly a ruler of one of the Eighteen Kingdoms during the transition period from the Qin dynasty to the Western Han dynasty, before Liu Bang's general, Han Xin, conquered his territory, capturing him and his capital city based in Zhaoge in the process. In the early Han dynasty, Sima Ang's former kingdom, which had been largely situated in Henei, became a commandery of the Han Empire, and his descendants had lived there since.