Ketil was the son of Thorkel of Namdalen, Jarl of Namdalen, and Hrafnilda, the daughter of Ketil Trout of Hrafnista. Ketil was a man of great wealth and a close friend and cousin of Thorolf Kveldulfsson and his brother Skalla-Grimr.
When he heard that Harald I of Norway was launching an attack against Thorolf, Ketil was among the latter's allies who set out to support him. They arrived too late, and when the expedition arrived Thorolf had already been slain. In retaliation for Thorolf's death, Ketil gathered sixty warriors and raided Torgar, home of Harek and Hrærek (the sons of Hildirida), who had slandered Thorolf to the king. Following this raid, Ketil loaded his allies, family and possessions onto two large longships and set sail for Iceland. They settled for the first winter on the eastern bank of the outer Rang River, but later moved eastwards and took land between "Thjors-river and Mark-fleet, from fell to firth, and made his home at Hof by east Rang-river.