The disorder in Germany after the fall of the Hohenstaufen afforded an opportunity for Rudolph to increase his possessions.
He was attached to the Hohenstaufen by the marriage of his daughter, Elizabeth, with Conrad, son of Frederick II.
He was the uncle and guardian of Conradin of Hohenstaufen, whom he assisted to make his journey to Italy in 1267, and accompanied as far as Verona.
Having married Constance, daughter of Manfred of Beneventum, he came forward as the representative of the claims of the Hohenstaufen in Naples and Sicily against Charles, duke of Anjou.
Determined to destroy the power of the Hohenstaufen in Italy, and offered the kingdoms of Naples and Sicily, in consideration of a yearly tribute, to Charles of Anjou, in opposition to Manfred, the bastard son of the late emperor Frederick II.