Son of Vortigern and brother of Vortimer, Catigern, and Pascentius. Faustus was Vortigernís son by Vortigernís own daughter, though P.F.J. Turner believes she was his step-daughter.

Nennius mentions him in connection with St. Germanus, who baptized and raised him, and he eventually founded a monastery on the banks of the river Riez.