Nepotianus was the son of Eutropia, half-sister
of Emperor Constantine I, and of Virius Nepotianus. On his mother's side, he was the grandson of Emperor Constantius Chlorus and Flavia Maximiana Theodora.
Mosaic showing grape harvesting, Santa Costanza Mausoleum, Via Nomentana, Rome,
Following the revolt of Magnentius, Nepotianus proclaimed himself "emperor" and entered Rome with a band of gladiators on June 3, 350 AD.
After attempting to resist Nepotianus with an undisciplined force of Roman citizens, Anicetus (Praefectus urbi Titianus), prefect of the Praetorians of Rome and supporter of Magnentius, fled the city.
Magnentius quickly dealt with this revolt by sending his trusted magister officiorum Marcellinus to Rome. According to Eutropius, Nepotianus was killed in the resulting struggle
on June 30, 350 AD, his head put on a lance and borne around the city. In the following days, his mother Eutropia was also killed during the persecution of the supporters of Nepotianus, most of whom were senators.