Sima You the second son of Sima Zhao of the Kingdom of Wei following the Three Kingdoms Period of China. Sima You became the heir to his uncle, Sima Shi who at the time was childless. It is known that Sima You was a person of mild-mannered character who expected to be appointed as the king, but ended being passed over due to that of his young age. The heir that was chosen was Sima Yan, the first son of Sima Zhao who then established the Jin Dynasty not too long later after his succession.
((China-bio-stub}}
Source
Romance of the Three Kingdoms X official portrait list -- may be fictional