He was the son of Bran Ardchenn mac Muiredaig (died 795), a previous king.
[2] He is given the title leth-ri (one of two kings) at his death in 818 (Annals of Ulster) and ruled in conjunction with Muiredach mac Ruadrach (died 829) of the Uí Fáeláin sept.[3] In 795 his father, Bran, had been assassinated by his successor Fínsnechta Cethardec mac Cellaig (died 808) of the Uí Dúnchada sept as a direct challenge to the high-king.
[4] Finsnechta took refuge with Muirgius mac Tommaltaig (died 815), the King of Connacht who then aided him in recovering his throne in 806.
In 814 a battle is recorded between the Uí Cheinnselaig of south Leinster and the sons of Bran.
The battle was won by the sons of Bran,[6] probably Muiredach and his brother Cellach mac Brain (died 834).