This quest begins once you have pledged to Hordafylke from the alliance map at the longhouse in Ravensthorpe. More specifically, it will begin immediately after travelling to Norway during The Road to Valhalla. Now that you’ve returned to Norway with Sigurd, it’s time to find and speak with Styrbjorn, Sigurd’s blood father and Eivor’s adopted father.
To begin, you’ll need to sail to Alrekstad, just east of where you spawn in Norway. As you approach Alrekstad, bring your ship in at the docks and then make your way northeast through the town. You’ll find Styrbjorn in the same meadhall where you confronted Gorm, all those years ago. If you’re having trouble finding it, use your raven to scout it, and then Odin’s Sight as you draw nearer, to highlight the location in teal.
When you enter the meadhall a cutscene will begin, during which you’ll have a few dialogue options. It doesn’t matter what you choose here, as the outcome will be the same. After the scene, follow Sigurd back to the longship. You’ll have a few more dialogue options with Sigurd here. As before, choose as you wish. After the scene, you’ll need to sail to the northernmost fjord in Hordafylke, as shown in the screenshot above. When you reach the shore of the fjord, the quest will complete, immediately leading into A Brother’s Keeper.