Tryggve Olafsson - Wikipedia

Tryggve Olafsson was the son of Olaf Haraldsson, king of Vestfold and Vingulmark, and grandson of King Harald Fairhair. According to the Heimskringla, Tryggve performed Viking expeditions in Ireland and Scotland. In 946 King Haakon I of Norway went north, and set Tryggve to defend Viken against his enemies in the south. He also gave him all that he could reconquer of land in the area which, the summer before, King Haakon had subjected to payment of taxes. Historically the Danish kings had dominion over the area.

King Haakon was mortally wounded at the Battle of Fitjar in an engagement with Eirik’s sons. After Haakon's death, Harald Greycloak, third son of Eirik Bloodaxe, jointly with his brothers became kings of Norway. Tryggve was subsequently killed by Harald Greycloak as part of Harald's effort to establish his own rule over Norway.

Reportedly Tryggve was lured into a trap. His wife Astrid gave birth to their son shortly after. Tryggve's son, Olaf Tryggvason, later became king of Norway, and his daughter Ingeborg Tryggvasdotter married Ragnvald Ulfsson, the earl of Västergötland and later the ruler of Staraja Ladoga.