Somerled was the son of Gille-Brigde, son of Gille-Adomnain. He was also said to have been descended from Colla Uais, one of the legendary founders of the Airgialla in northern Ireland and from the Airgialla via Godfrey, son of Fergus, said to have been a contemporary of Kenneth mac Alpin (d.858). Somerled is first mentioned in 1153, then styled 'regulus' of Argyll, when he rebelled against King Malcolm IV (d.1165) with his nephews, the sons of Malcolm Macheth. He was reconciled with the king in 1160, but rebelled again in 1164, when, at Renfrew, he was killed in battle with his son, Gille Brigte, whom he fathered by an unknown woman. He had married Ragnhild, daughter of Olaf (d.1153), son of Godred, king of the Isles, and they had three sons, Dugald, Ranald, and Angus, and perhaps a fourth, Olaf. He also had a daughter, Bethoc, who was the first prioress of Iona Nunnery. Somerled may have founded the monastery of Saddell in Kintyre, though this was probably more the work of his son, Ranald. From Somerled's son, Dugald, are descended the lords of Argyll and the clan MacDougall, and from his son, Ranald, the MacDonald lords of the Isles and also MacRuaris.
W.D.H. Sellar, 'Somerled', ODNB [http://www.oxforddnb.com/view/article/26782]