 Referring to the "Privilegium Minus", Pope Innocent IV, against the feudal principle of patrilineal inheritance, confirmed the hereditary rights of Frederick's sister Margaret, widow of Henry of Hohenstaufen, and his niece Gertrude, widow of Ottokar's elder brother Přemyslid Margrave Vladislaus of Moravia who died in 1247.Upon the death of Gertrude's second husband, Margrave Herman VI of Baden, in 1250, Ottokar invaded the Austrian lands, acclaimed by the local nobility.To substantiate his claims, he married Margaret (about 30 years his senior) in 1252.