Dictionary of National Biography, 1885-1900/Iago ab Idwal ab Meirig
IAGO ab Idwal ab Meirig (d. 1039) king of Gwynedd, was, probably on account of his tender years, thrust aside from the succession on the death of his father, Idwal ab Meirig [q.v.], in 997. The usual struggle between rival claimants ensued, and among others, Llewelyn ab Seissyllt, who was not a member of the royal house, filled the throne for a period; but on his death, in 1023, Iago seized the sovereignty of Gwynedd, while that of Dyved fell to the hands of Rhydderch ab lestyn (Brut y Tywysogion, p.265). Iago gave refuge to Iestyn ab Gwrgant, who had violated Ardden, the daughter of Robert ab Seissyllt, and cousin of Gruflydd ab Llewelyn ab Seissyllt. The latter thereupon attacked Iago and killed him after an obstinate battle in 1039. (Annales Cambriæ; Brut y Tywysogion; Gwentian Chron.} Gruflydd then placed himself on the throne occupied at an earlier date by his father, Llewelyn ab Seissyllt.
[See authorities cited.]