Óláfr was a member of the Crovan dynasty, and a son of Guðrøðr Óláfsson, King of Dublin and the Isles. Óláfr's mother was Fionnghuala Nic Lochlainn. Guðrøðr had several other children: Affrica, Rǫgnvaldr, and Ívarr. Other possible children include Ruaidhrí, and a daughter whose name is unknown. According to the thirteenth-century "Chronicle of Mann", Óláfr's mother was Fionnghuala Nic Lochlainn, granddaughter of Muirchertach Mac Lochlainn, High King of Ireland. She was probably a daughter of Muirchertach's son, Niall Mac Lochlainn, King of Cineál Eoghain. Although Óláfr's parentage is known, the maternal ancestry of Rǫgnvaldr is less certain. She may have been Sadbh, an Irishwoman identified as his mother by a contemporary Gaelic praise poem. The likelihood that Rǫgnvaldr and Óláfr had different mothers may well explain the intense conflict between the two men in the years that followed.