Sigtrygg may have succeeded his paternal half-brother Glúniairn as king of Dublin in 989, but it is just as likely his rival Ivar of Waterford came to power in the city then. The Irish annals record little information about Sigtrygg, his family or Dublin during these first five years of his reign. Benjamin Hudson claims this was because of the arrival of the future King of Norway, Olaf Tryggvason, who took up residence in Dublin for a few years after marrying Sigtrygg's sister Gytha. Tryggvason had met Gytha while raiding along the coasts of the Irish Sea. The presence of a powerful Viking leader in Dublin was a deterrent to Irish raids, and Trygvason may have weakened Sigtrygg's foes by plundering them.