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Sima Yang (司馬羕) (before 227 - 25 July 291), courtesy nameZiyi (子翼), formally Prince Wencheng of Ru'nan (汝南文成王), was briefly a regent during the reign of Emperor Hui during the Western Jin dynasty.
While Sima Liang's birth year is not recorded, it is recorded in volume 38 of Book of Jin that he was older than his full-brother Sima Zhou, who was born in 227. At the same time, he was younger than his half-brother Sima Zhao, who was born in 211.
According to Sima Zhong's biography in the Book of Jin, Sima Wei was killed on the yichou day in the 6th month of the 1st year of the Yongping era of Emperor Hui's reign. This corresponds to 26 Jul 291 in the Gregorian calendar. Book of Jin, vol. 4. In Sima Wei's biography, it was recorded that he was killed the day after Sima Liang died. (「會天明……遂斬之」, Book of Jin, vol. 59)