Gleb of Murom
Boris and Gleb, Christian names Roman and David, were the first Russian saints. According to two 11th century Lives of Boris and Gleb (assigned to Nestor the Chronicler and Jacob the Monk), they were children of Vladimir the Great who liked them more than his other children. Both were murdered during the internecine wars of 1015-1019 and glorified by the Russian Orthodox church in 1071. Numerous churches are dedicated to them, e.g., the Borisoglebsky Abbey near Rostov.
The Primary Chronicle says that their mother was a Bulgarian woman, and their Turkic names seem to back up this information. Most modern scholars, however, argue that Boris and Gleb had different mothers, and were of different age. Boris, who had been already married and ruled the town of Rostov, was probably regarded as an heir apparent to the Kievan Rus throne. Gleb, who was still a minor, ruled the easternmost town of Murom.
The Russian Primary Chronicle blamed Svyatopolk the Accursed for plotting their assassination. Boris and his manservant were stabbed to death when sleeping in a tent. The prince was discovered still breathing when his body was being transported in a bag to Kiev, but the Varangians put him from his misery with a thrust of a lance.
Gleb was assassinated on his way to see the dying father by his own cook who cut his throat with a kitchen knife and concealed his body in a brushwood. The Life contains many picturesque details of Boris and Gleb's last hours, such as their sister's warning about the murderous plans of Svyatopolk.
It doesn't stand to reason to accept the Life's data at face value. This masterpiece of hagiography unites numerous literary traditions. Actual circumstances of Boris and Gleb's life and death might have been different. Perhaps the crucial evidence comes from several unbiased foreign sources which mention that Boris succeeded his father in Kiev, and was not lurking in Rostov as the Russian Primary Chronicle seems to imply.
Moreover, the Norse Eymund's saga tells a story of the Varangian warriors who were hired by Yaroslav I the Wise to kill his brother Boris. Some historians trusted the saga more than Russian sources, claiming that it was Yaroslav (and not Svyatopolk) who was interested in removing his political rivals and was therefore guilty of his brothers' murder.