Why do we celebrate the feasts of St. Philip and St. James the Less on the same day? Because they were both apostles? No, we celebrate them on the same day because their relics were brought to Rome together on the same day in early May. They rest there still, in the Basilica of the Holy Apostles.
Both were apostles, and both served Christ faithfully during the very early days of the Church.
James was martyred in Jerusalem around Passover during the time Nero was Emperor of Rome. Philip was killed in Greece under the reign of the Roman emperor, Domitian.
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