Sts Nereus, Achilleus, Domitilla and Pancratius

Not much is known of these...they died too early, and little information survived...except that they were likely to have been soldiers turned pacifists who were killed for their refusal to fight...from here:

The commemoration of these four Roman saints is made by the Church on 12 May, in common, and all four are named in the Proper of the Mass as martyrs. The old Roman lists, of the fifth century, and which passed over into the Martyrologium Hiernoymianum, contain the names of the two martyrs Nereus and Achilleus, whose grave was in the Catacomb of Domitilla on the Via Ardeatina; in the same calendar was found the name of St. Pancratius, whose body rested in a catacomb on the Via Aurelia.