His father was king of Norway from 1142 to 1157, ruling as co-ruler with his brothers, Inge Haraldsson and Sigurd II Munn.
Eystein II was killed in 1157 during the power-struggle against his brother, Inge, in an early stage of the civil war era in Norway.
Haakon was defeated and killed by Jarl Erling Skakke at Sekken near the town of Veøya in Romsdalen during 1162.
The Birkebeiner took the city of Trondheim and proclaimed Eystein to be king at the Øretinget Thing by the mouth of the river Nidelva in during 1176.
The background for these conflicts were the unclear Norwegian succession laws, social conditions and the struggle between Church and King.