Apostles
Later in the Gospel narratives the twelve apostles are described as having been commissioned to preach the Gospel to "all the nations", regardless of whether Jew or Gentile. Paul emphasized the important role of the apostles in the church of God when he said that the household of God is "built upon the foundation of apostles and prophets, Christ Jesus himself being the cornerstone".
Although not one of the apostles commissioned during the life of Jesus, Paul, a Jew named Saul of Tarsus, claimed a special commission from the risen Jesus and is considered "the apostle of the Gentiles", for his missions to spread the gospel message after his conversion. In his writings, the epistles to Christian churches throughout the Levant, Paul did not restrict the term "apostle" to the Twelve, and often refers to his mentor Barnabas as an apostle. The restricted usage appears in the Revelation to John.
Epistle of James
The writer of the letter of James identifying himself as "a servant/slave of God and of the Lord Jesus Christ" is much the same as the author of the Epistle of Jude did by calling himself "a slave of Jesus Christ, but a brother of James" (Jas 1:1; Jude 1). Furthermore, the salutation of his letter concludes with the term “greetings" (Greek χαίρειν), much like the letter on circumcision that was sent to the congregations. In the latter instance it was apparently Jesus's brother, James, who spoke prominently in the assembly of "the apostles and the older men" at Jerusalem. Some have said the authorship of this epistle points to James, the brother of Jesus, to whom Jesus evidently had made a special appearance after his resurrection described in the New Testament as this James was prominent among the disciples.