Guttorm was an illegitimate son of
Sigurd Lavard and thus a grandson of King
Sverre. The identity of his mother is unknown. Sigurd predeceased his father, Sverre, who died in 1202 and was succeeded by his younger son
Haakon Sverresson. Haakon reigned until his own death on 1 January 1204. Haakon had pursued a policy of peace and reunification between the
Birkebeiner and
Bagler during his short reign, but following his death relations between the parties collapsed and a new phase of the
Norwegian civil wars began. Parts of the Birkebeiner were disgruntled by Haakon's policy of reconciliation with the Bagler, which may have led to his death, following which the balance of power within the Birkebeiner switched immediately to the faction around
Haakon the Crazy. The day after Haakon's death, the Birkebeiner designated Guttorm as king at a meeting of the
hird, in consultation with Bishop Martin of
Bergen. Sverre's nephew Haakon the Crazy was simultaneously appointed
regent as leader of the hird and the army. According to the
Bǫglunga sǫgur (Bagler sagas), the young king then took a sword and mounted it to Haakon's side, and handed him a shield. He further gave Haakon the title of earl, with consent from all the chieftains, and had Haakon sit next to him at his throne. Haakon's unusually strong position was thus symbolised by his sitting at the same level as the king, and not on a lower seat as would have been customary for an earl. Another of Sverre's nephews, Peter Støyper, together with
Einar Kongsmåg, husband of Sverre's daughter Cecilia, were appointed as Guttorm's guardians. ==Revolt and death==