 He belonged to the main ruling dynasty of the Dál nAraidi known as the Uí Chóelbad based in Magh Line.He ruled as king of the Dál nAraidi from 824/849-873 and as leth-ri (co-king) of Ulaid from 857-871 and sole king of Ulaid from 871-873.Lethlobar first appears in the annals in the year 828 when he inflicted a battle-route on the Vikings.