The patriarch of Aquileia Sigeard, quoted in ancient sources as Syrius, was a son of Sigeard IV (Sizo), count of Pongau, and Pilihilde, who descended from the Andechs, another important family of the high Bavarian nobility. He is mentioned for the first time in 1048, that is to say after the death of his father who had fallen in a battle in 1044, during a military expedition of king Henry III against Hungarians. His position as a priest, as well as the Sighardinger’s loyalty towards the Salian dynasty opened to Sigeard the way to the court chapel. The following emperor, Henry IV, appointed him chancellor, an office that allowed him to rule over the royal chancellery from 24 February 1064 to August 1067, when Henry IV, after patriarch Rabenger’s death († 18 february 1068), appointed him patriarch of Aquileia. On the burst of the investiture contest in 1075, despite the traditional policy of his family and distinct from the majority of other German bishoprics, the patriarch of Aquileia Sigeard took the part of Gregory VII. As a papal legate he took part in the Diet of the German princes summoned at Tribur in October 1076, where they decided that they would refuse to acknowledge Henry IV as their king, was he not reconciled to the pope within February of the following year. This decision was followed by Henry IV’s dramatic expedition to Italy where, at the end of January 1077, at Canossa, he obtained the revoke of his excommunication and could bring the Aquileian patriarch Sigehard to his part. Most likely at the beginning of April 1077, at Pavia Sigeard received Henry IV’s privilege through which the king donated him and the Aquileian Church the County of Friuli with the pertaining feoff, and the regalia, rights and revenues of the county. After celebrating Easter of that year at Aquileia and going back to Germany, on 11 June, at Nuremberg, Henry IV granted the Aquileian Church other two important privileges, since he donated also the County of Istria and the March of the Carniola. Sigeard had then in his hands three counties that controlled the access way to Italy from the East; their union formed one only wide territory that very much reminded of the great Carolingian March of Friuli at the beginning of the ninth century. However the patriarch could not enjoy his success for long time: on 12 August 1077 he suddenly died in his way back from Germany, in the nearby of Ratisbon. His remains were translated to Aquileia and buried in the basilica near the Holy Sepulchre.
For further information see the entry Sighardinger (di) Sigeardo, patriarca d’Aquileia written by Peter Štih in Nuovo Liruti. Dizionario biografico dei Friulani, 1, Il Medioevo, edited by C. Scalon, Udine, Forum, 2006, 782-789.