This Arnulf (Arnoul) passed his earlier life at the court of Theodebert II, king of Austrasia; through the marriage of his elder son with a daughter of Pepin of Landen (St. Begga), he became an ancestor of the Carolingian dynasty.
At the age of thirty, he wanted to retire from public life,
but instead in 614 he was chosen Bishop of Metz, though still a layman. He continued to act as adviser to King Chlotar II, whom he had helped to the Frankish throne, and was tutor to his son Dagobert.
Arnulf made further attempts to resign his offices, but it was not till 629 that he was able to retire to the Vosges mountains. Here his friend St. Romaric had preceded him and begun the monastic community at Habend that was later called Remiremont. St. Arnulf settled near by, and lived there till his death twelve years later.
-The Avenel Dictionary of the Saints, Donald Attwater (New York; Avenel Books, 1965).