Boris

Boris was the son of Vladimir I, Grand Duke of Russia, Olga was his great-grandmother. After the death of Vladimir I, Boris and his youngest brother Gleb were murdered in the turmoil and disputes over the heir to the throne. Historically, the question of guilt is unresolved. According to church tradition, Boris’ half-brother Svyatopolk seized the capital Kiev after the death of his father and had Boris killed, who – on a military campaign against the rebellious Turkish people of the Pechenegs – had the largest force. Immediately afterwards, he arranged for the murder of Boris’ youngest brother Gleb. Sviatoslav, another brother, had fled to the Carpathians, but he also died under the knives of his henchmen. Boris was probably canonized together with Gleb on May 2, 1072, when her bones were transferred to the newly consecrated Boris and Gleb Church in Vyshhorod near Kiev. They are the first saints of the Russian Church. In 1724, Pope Benedict XIII confirmed the cult for the Catholic Church as well.

Joachim Schäfer: Article Boris, from the Ecumenical Dictionary of Saints: https://www.heiligenlexikon.de/BiographienB/Boris.html