Today is the feast day of two martyrs who were twins, Saints Medard and Gildard. They were not only born on the same day but they were consecrated bishops on the same day and they died on the same day. That was in northern France in 558.
Other twin saints who graced the Church in the sixth century were Saints Benedict and Scholastica who died in 543 only forty days apart. Other noted twins among the saints are: Saints Crispin and Crispinian, who were martyred together under the Diocletian persecution in 285. They also labored in northern France in the city of Siossons. Twin Saints Mark and Saint Marcellian, Roman deacons, also suffered martyrdom in the Diocletian persecution. Their feast day is June 18, one day before the feast day of the twins, Saints Gervase and Protase. Gervase and Protase are considered the protomartyrs of Milan having shed their blood for Christ in the year 165. However, their mother, Valeria, is believed to have been martyred before them in Milan. Their father, Vitalis, was also martyred, not in Milan, but in Ravenna. Their relics were miraculously discovered through a dream given to Bishop of Milan, Saint Ambrose, in 386. Saint Augustine, as an eye witness, wrote in his Confessions about the discovery of the relics and the miracles that accompanied their transfer to the cathedral.
Then we have the twins Saints Cosmas and Damian who are the last two men mentioned in the canon of the Mass before the Pater Noster. They were physicians from Syria. Dedicated to relieving the suffering of the poor, they took no payment for their services. They, too, suffered martyrdom under Diocletian in the year 303 along with their three other brothers Anthimus, Leontius, and Euprepius.
Does anyone know of other canonized twins?