[1] On the death of his father in 1204, he succeeded him as Duke of Merania, while the margravial titles in Istria and Carniola were inherited by his younger brother Henry II.

Otto's brother Henry II was accused of having been involved in Philip's assassination and his estates were seized by Duke Ludwig I of Bavaria.

In 1217 Otto had joined the Babenberg duke Leopold VI of Austria and his brother-in-law King Andrew II of Hungary in the Fifth Crusade.

[3] In 1222, a dispute arose with Gerard I de Rougemont, the Archbishop of Besançon over the building of a castle which violated a vow taken by his predecessor, Otto I of Burgundy (d.1200).

[4] When Otto failed to raze the castle or give an explanation for his actions, the archiepiscopal court excommunicated him and placed his lands under interdict.