Rudolf I of Germany
Otto was a son of Duke Meinhard of Carinthia and his wife Elisabeth of Bavaria, widow of the Hohenstaufen king Conrad IV of Germany. His father was enfeoffed with the Carinthian duchy by King Rudolf I of Germany in 1286, in turn for his support of the Habsburgs against King Ottokar II of Bohemia. Otto's sister Elizabeth was married to Rudolf's son Albert of Habsburg and became German queen in 1298.