Boris and Gleb
Saint Nestor the Chronicler (; 1056 – c. 1114, in Principality of Kiev, Kievan Rus') was the reputed author of the "Primary Chronicle" (the earliest East Slavic letopis) "Life of the Venerable Theodosius of the Kiev Caves", and "Account about the Life and Martyrdom of the Blessed Passion Bearers Boris and Gleb."