The story of how Eysteinn's father came to the kingship is similar to that of Eysteinn.
At some point in the 1120s, Haraldr gilli arrived in Norway claiming to be a brother of the reigning king.
The tale of Haraldr gilli's accession is preserved in several sources.
According to Magnússona saga, within Heimskringla, a Norwegian baron named Hallkell húkr voyaged from Norway to the Isles where he encountered Haraldr gilli and his mother.
Named Gillikristr by the saga, Haraldr gilli told Hallkell húkr that he was a son Magnús berfættr, King of Norway (died 1103), and that another name of his was Haraldr.
In fact, Haraldr gilli's byname—gilli—is a shortened form of Gillikristr, an Old Norse form of the Gaelic personal name Gilla Críst.
According to Magnússona saga, Haraldr gilli was originally from Ireland, and both he and his mother were subsequently conveyed to Norway by Hallkell húkr, who presented them to Magnús' reigning son, Sigurðr Jórsalafari, King of Norway (died 1130).
Fagrskinna and Morkinskinna give similar accounts, with the latter source calling him Haraldr Gillikristr.
Some years before his arrival, whilst only a teenager, the thirteenth-century Orkneyinga saga indicates that Haraldr gilli encountered Kali Kolsson (died 1158) at Grimsby, where he revealed to Kali his parentage, as a descendant of Magnús and an Isleswoman.
According to Magnússona saga, and the twelfth-century Historia de antiquitate regum Norwagiensium, after Haraldr gilli's arrival in Norway from Ireland or Scotia respectively, Sigurðr Jórsalafari had Haraldr gilli undergo an ordeal in which the latter was to walk upon nine red-hot ploughshares.
The latter source further states that it was believed that Haraldr gilli was divinely aided since he emerged from his ordeal unburnt.

Since Haraldr gilli's mother evidently travelled with him to Norway, and Sigurðr Jórsalafari is known to have spent time in Ireland as a child, it is possible that Sigurðr Jórsalafari recognised her as a former lover of his father.
The accounts of Eysteinn's father gaining royal recognition illustrate that, although such claimants sometimes had to undergo ordeals to prove their paternity, the testimony of their foreign mothers also carried weight in the final decision.
Nevertheless, not only did claimants to throne need to prove their paternity, they needed to also gain the acceptance of an assembled þing in a process known as konungstekja.
Having gaining approval of such an assembly, a successful claimant would have sworn an oath to uphold the national law, whereupon he would have received an oath of allegiance from the assembly itself.
Eysteinn and Haraldr gilli lived during a remarkable period of Norwegian history in which civil warring waged for nearly a century, from 1130 to 1240.
No less than forty-six candidates emerged seeking recognition as king during this period.
Although twenty-four of these candidates succeeded, only two gained royal authority throughout the realm.
In fact, only one king from this period, Ingi, was the legitimate son of a king.
The story of how Eysteinn's father came to the kingship is similar to that of Eysteinn. At some point in the 1120s, Haraldr gilli arrived in Norway claiming to be a brother of the reigning king. The tale of Haraldr gilli's accession is preserved in several sources. According to Magnússona saga, within Heimskringla, a Norwegian baron named Hallkell húkr voyaged from Norway to the Isles where he encountered Haraldr gilli and his mother. Named Gillikristr by the saga, Haraldr gilli told Hallkell húkr that he was a son Magnús berfættr, King of Norway (died 1103), and that another name of his was Haraldr. In fact, Haraldr gilli's byname—gilli—is a shortened form of Gillikristr, an Old Norse form of the Gaelic personal name Gilla Críst. According to Magnússona saga, Haraldr gilli was originally from Ireland, and both he and his mother were subsequently conveyed to Norway by Hallkell húkr, who presented them to Magnús' reigning son, Sigurðr Jórsalafari, King of Norway (died 1130). Fagrskinna and Morkinskinna give similar accounts, with the latter source calling him Haraldr Gillikristr. Some years before his arrival, whilst only a teenager, the thirteenth-century Orkneyinga saga indicates that Haraldr gilli encountered Kali Kolsson (died 1158) at Grimsby, where he revealed to Kali his parentage, as a descendant of Magnús and an Isleswoman. According to Magnússona saga, and the twelfth-century Historia de antiquitate regum Norwagiensium, after Haraldr gilli's arrival in Norway from Ireland or Scotia respectively, Sigurðr Jórsalafari had Haraldr gilli undergo an ordeal in which the latter was to walk upon nine red-hot ploughshares. The latter source further states that it was believed that Haraldr gilli was divinely aided since he emerged from his ordeal unburnt.
Since Haraldr gilli's mother evidently travelled with him to Norway, and Sigurðr Jórsalafari is known to have spent time in Ireland as a child, it is possible that Sigurðr Jórsalafari recognised her as a former lover of his father. The accounts of Eysteinn's father gaining royal recognition illustrate that, although such claimants sometimes had to undergo ordeals to prove their paternity, the testimony of their foreign mothers also carried weight in the final decision. Nevertheless, not only did claimants to throne need to prove their paternity, they needed to also gain the acceptance of an assembled þing in a process known as konungstekja. Having gaining approval of such an assembly, a successful claimant would have sworn an oath to uphold the national law, whereupon he would have received an oath of allegiance from the assembly itself. Eysteinn and Haraldr gilli lived during a remarkable period of Norwegian history in which civil warring waged for nearly a century, from 1130 to 1240. No less than forty-six candidates emerged seeking recognition as king during this period. Although twenty-four of these candidates succeeded, only two gained royal authority throughout the realm. In fact, only one king from this period, Ingi, was the legitimate son of a king.
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