more immediate forebears, most recently his great-grandfather Domnall mac Cellaig (died 974), had been counted among the kings of the Uí Cheinnselaig. Diarmait's mother was Aife, daughter of Gilla Pátraic mac Donnchada, king of Osraige. He had at least one sibling, a brother named Domnall whose son Donnchad mac Domnaill Remair later became king of Leinster.