Ernesius was the nephew of William of Malines,[1] who came from Flanders and was appointed Latin patriarch of Jerusalem by King Baldwin II.
[5] As Fulcher's chancellor, Ernesius supported Queen Melisende in her struggle against King Baldwin III.
[6] Ernesius had originally opposed the appointment of Amalric of Nesle to the patriarchate (in 1157 or 1158), but he eventually began cooperating with him.
[13] In 1169 an embassy consisting of Patriarch Amalric, Archbishop Ernesius, and Bishop William of Acre was tasked with carrying letters from King Amalric to Emperor Frederick Barbarossa, Kings Louis VII of France and Henry II of England, Queen Margaret of Sicily, and Counts Philip I of Flanders, Theobald V of Blois, and Henry I of Champagne.
The prelates were driven back to Acre by a severe storm after two days at sea; due to the risk, they refused to set sail again.