 Bróðir and Óspak of Man were two Danish brothers who were active in the Isle of Man and Ireland in the 11th century . They are mentioned in the 12th century Irish Cogadh Gaedhil re Gallaibh and the 13th century Icelandic Njal 's Saga as key leaders who fought on opposite sides in the Battle of Clontarf in 1014 . The latter account names Bróðir as the killer of Brian Boru , the High King of Ireland . Both Boru and Bróðir died in the battle , although accounts differ as to who killed whom . Óspak fought on the side of Boru , was injured , and lost his two sons in the battle . 
