Catholic Encyclopedia (1913)/Sts. Mark and Marcellian
Martyred at Rome under Diocletian towards the end of the third century, most likely in 286. These martyrs, who were brothers, are mentioned in most of the ancient martyrologies on 18 June, and their martyrdom is known to us from the Acts of St. Sebastian, which, though in great part legendary, are nevertheless very ancient. Cast into prison for being Christians, they were visited by their father and mother, Tranquillinus and Martia, who, being still idolaters, implored them to return to the worship of the false gods to save their lives. But Sebastian, whose approaching martyrdom was to render him illustrious, having penetrated into their prison at the same time, exhorted them so earnestly not to abandon the Christian Faith, that he not only rendered their fidelity immovable, but also converted their parents and several of their friends who were present. The judge, before whom they were at length brought, not being able to induce them to apostatize, condemned them to death. They were buried in the Via Ardeatina, near the cemetery of Domitilla. Their bodies were translated at a later date (which is not quite certain, but probably in the ninth century) to the church of Sts. Cosmas and Damian, where they were rediscovered in 1583 in the reign of Gregory XIII. They still rest there in a tomb, near which may be seen an ancient painting wherein the two martyrs are represented with a third person who seems be the Blessed Virgin.