William II of Sicily
She married the Doge Pietro Ziani in 1213, after the death of his former dogaressa Maria Baseggio. The marriage was arranged on the suggestion of the doge as a confirmation and renewal of the Treaty of Venice between Sicily and Venice, which had been forged by the father of Pietro Ziani, doge Sebastiano Ziani, and William II of Sicily, the predecessor of Constance's father. This was the first time a Doge of Venice had married a Princess since Theodora Anna Doukaina Selvo in the 11th-century.