Kristín had an incestuous relationship with her brother Gísli, who was also in a relationship with their sister Þórdís. When the three were found out, they fled to the sanctuary of the Skálholt Cathedral, as the punishment for incest at the time was execution. The sibling’s brother Oddur was chief steward at Skálholt for Bishop Gísli Jónsson and Oddur thought highly of all three siblings. The BIshop arranged absolution for Kristín with the King, and Kristín would later marry the Bishop and had a number of children by him. (The outcomes for Gísli and Þórdís aren’t recorded.)

This story appears to be recounted in Espólín’s Annals, chapter 3 pages 104-105.