The context in Matt. 13:55 and Mk. 6:3 does strongly suggest a familial relationship, but calling Joseph, Simon, James, and Judas Jesus’s "brothers" makes them no more His biological siblings than calling Jesus the "the carpenter's Son" makes Joseph His biological father.
· "Is this not the carpenter’s Son? Is not His Mother called Mary?
Are not James and Joseph and Simon and Judas His brothers?" (Matt. 13:55)
· "Is this not the carpenter, the Son of Mary, and
the brother of James and Joses and Judas and Simon?" (Mk. 6:3)
· "Then after three years,
I did go up to Jerusalem to become acquainted with Cephas (Peter), and I stayed with him for fifteen days.
However, I did not set eyes on any of the other apostles, except for James, the brother of the Lord" (Gal. 1:18-19)
The Koine Greek word
ἀδελφός (
adelphos), usually translated as 'brother' in English, has a wide range of definitions: "a brother, near kinsman, or relative, e.g., cousin, nephew, etc.", "a fellow countryman", "a fellow member of the Christian community", or "an associate". In the plural, ἀδελφοί (
adelphoi) often functions as a gender-inclusive term meaning "brothers and sisters".
Contextual evidence strongly suggests that the James mentioned in the Gospels (Matt. 13:55; Mk. 6:3) and by Paul (Gal. 1:19) was the same individual—a kinsman/relative of Jesus who was also one of the Twelve Apostles. Given that there were only two apostles named James (of Zebedee and of Alphaeus), and that the latter had a brother named Judas (Jude/Thaddeus), it is reasonable to conclude that James son of Alphaeus was the 'Lord’s brother' referenced in early church tradition.
Additionally, there's another Mary, the sister-in-law of Jesus's Mother, and wife of Clopas/Cleophas, who was the mother of at least two sons named "James" and "Joseph":
· “When the Sabbath was past, Mary Magdalene, and
Mary (of Clopas/Cleophas) the mother of James (the Less), and Salome (the mother of the sons of Zebedee), bought spices, so that they might come and anoint him” (Mk. 16:1)
· Now they were Mary Magdalene, Joanna, and
Mary (of Clopas/Cleophas) the mother of James (the Less). The other women with them told these things to the apostles" (Lk. 24:10)
· “Mary Magdalene,
Mary (of Clopas/Cleophas) the mother of James (the Less) and Joseph, and the mother of the sons of Zebedee (Salome)” (Matt. 27:56)
· “Mary Magdalene,
Mary (of Clopas/Cleophas) the mother of James the Less and Joseph, and Salome (the mother of the sons of Zebedee)” (Mk. 15:40)
· “His Mother (Mary of Joseph), His (Jesus's) Mother’s sister
Mary, the wife of Clopas/Cleophas (and the mother of James the Less and Joseph), and Mary Magdalene” (Jn. 19:25)
Lastly, what is your reason for not wanting to discuss the writings of the early Church Fathers on this topic, one of whom wrote that Joseph, Simon, James, and Judas were the sons of Mary and Clopas/Cleophas (or Alphaeus), and thus Jesus's cousins?