All of these Apostles are mentioned in the New Testament. Sosthenes was the ruler of the Synagogue in Corinth, and was converted through the preaching of St Paul. After traveling with St Paul for years, he became Bishop of Colophon near Ephesus. Apollos was a Jew from Alexandria, well educated and with a deep knowledge of the Scriptures. He was brought to the fulness of the Christian faith by Priscilla and Aquila in Ephesus, and went out preaching the Gospel among the pagans. His eloquence was so admired that for awhile the gentile Church divided into two factions, one for Paul and one for Apollos. Saint Apollos later became Bishop of Caesarea.
(The Synaxarion lists Cephas and Caesar here; but some believe that St Paul’s reference to Cephas in 1 Cor 1:12 refers to the Apostle Peter, not to a separate companion of St Paul; and that “those of Caesar’s household” (Phil. 4:22) refers to Christians in the Emperor’s palace in Rome, not to a Christian named Caesar.)