Flavus was the older brother of the Cherusci warloes Arminius. Flavus is the Latin for "blond," his real name is unknown. The brothers entered services with the Roman Empire serving as auxiliaries during the Pannonian uprising. Flavus remained loyal to Rome during the rebellion raised by Arminius and the subsequent Battle of the Teutoburg Forest. He participated in the punitive expedition sent by Tiberius against Arminius in AD 14-16.