The Annals of Inisfallen state 1027 - Muiredach Ua Flaithbertaig besieged Cathal, son of Ruaidrí, on Inis Crema in Loch Oirbsen, and divided his land despite him.
Muireadhach was a grandson of Flaithbheartach, hence his suffix, which would become the surname Ua/Ó Flaithbheartaigh/O'Flaherty.
The genealogies name his father as Maelcairearda; a person of this name died in 993, listed a king of Uí Briúin, but not explicitly as king of Uí Briúin Seóla.
He is listed as having three sons – Ruaidhrí of Lough Cimbe, Donagh Aluinn and Aedh.
From Ruaidhrí and Donagh would descended the eastern and western Ó Flaithbheartaigh's of Connemara.