As a rule, whenever St. Peter has a feast day, St. Paul is, likewise, commemorated. Next week we will celebrate the Conversion of St. Paul on January 25. On that day we will also commemorate St. Peter. Later in the year, on June 29, we will again remember these two apostles with the Feast of the Saints Peter and Paul. Just as they were joined in life in the heroic work of our Lord, joined in receiving the crown of martyrdom on the same day, and joined in honor in heaven, it is tradition that the two Founders of the Roman Church can never be divide.
Taken From: Butler’s Lives of the Saints
Eleven years after the ascension of Our Blessed Lord, St. Peter who had been appointed the head of the Church on earth by Christ Himself, transferred the seat of the Papacy from Antioch to Rome, where he preached the Faith and established his episcopal chair, and there the Bishops of Rome have been ever since accounted his successors. The feast of the Chair of St. Peter is that of the foundation of the See of Rome. From the Third Century it was symbolized by a chair carved in wood or tufa, a relic now kept high in the apse of the Vatican Basilica.
Taken from: Butler’s Lives of the Saints
A commemoration is likewise made of St. Prisca, a noble Roman virgin who suffered martyrdom about the year 275. Her relics are preserved in the ancient church in Rome which bears her name.
(Source: Fr. Lasance, The New Roman Missal)