Like many of the early martyrs, not much is known of Saints Marcellinus and Peter, except that they died for the Faith, put to death by beheading at the 12th milestone on the Via Aurelia outside of Rome, during the persecution of Diocletian in 304, and that their executioner, Dorotheus went on to convert to Christianity, according to the later Pope Damasus I (+384), who built a tomb and a church dedicated to the martyrs. Marcellinus was likely a priest, while Peter, an exorcist, back when that was a minor order with an actual spiritual function.
The story is that the two joyfully cleared the spot where they were to be killed, overgrown as it was with brambles and thornbushes – a fitting image of the spiritual life. Devotion to the martyrs spread throughout the early Church, their catacombs – where they were buried underground, along with many other Christians – became a place of pilgrimage. Emperor Constantine built a magnificent basilica over the spot, after the initial church was destroyed by the Goths. Churches sprang up across Europe with these martyrs as patrons, and their names appear in the Roman canon – quite the honour, signifying that whoever they were in life, God has called them higher, as He will all of, if we too remain faithful unto the end.
Saints Peter and Marcellinus, orate pro nobis!