Wenceslaus I of Bohemia
Ottokar was the second son of King Wenceslaus I of Bohemia (reigned 1230–1253). Through his mother, Kunigunde, daughter of Philip of Swabia, he was related to the Holy Roman Emperors of the Hohenstaufen dynasty, which became extinct in the male line upon the execution of King Conradin of Sicily in 1268.