She was a daughter of King Domnall Mór Ua Briain of Thomond (died 1194).
Her ancestors included High King of Ireland Niall of the Nine Hostages (fl.
Mór married Cathal Crobdearg Ua Conchobair, who ruled as King of Connacht in opposition (1189–1202) and solely (1202–24).
The marriage was unusual as she was Cathal's only wife; in contrast, most Gaelic rulers had a number of wives at the same time.
The senior line of the family, O'Conor Don - who survives to this day - descend from her.