According to John's Gospel Jesus on the cross committed his mother to the care of the Beloved Disciple, not to his brother, James. Admittedly James was not there. However, I wonder if this indicates that Mary was Joseph's second wife (as some have said) and that James was the Son of Joseph but not of Mary and Jesus was her only child. I know there are differences among churches about the duration of Mary's virginity, and proposals that Joseph also was a lifelong virgin, but I am looking for opinions that do not rely on dogma.
Jesus’ Mother and Brothers
46 While Jesus was still talking to the crowd, his mother and brothers stood outside, wanting to speak to him. 47 Someone told him, “Your mother and brothers are standing outside, wanting to speak to you.” 48 He replied to him, “Who is my mother, and who are my brothers?” 49 Pointing to his disciples, he said, “Here are my mother and my brothers. 50 For whoever does the will of my Father in heaven is my brother and sister and mother.” (Matthew 12:46-50)
Because John the beloved does the will of Jesus' Father in heaven. That is why Jesus made John His brother (as Mary's son).
So, this was the reason why John (the beloved) became Jesus' brother (or Mary's son) and his mother Mary. The crowd knew Jesus' brothers, and so they are his biological brothers including James (Matthew 13:55).
The reason for committing Mary to the Apostle John, rather than to James the brother of Jesus is because James was not a believer. John was. John was at the cross, James was not.
Now the Jews' feast of tabernacles was at hand. His brethren therefore said unto him, Depart hence [from Galilee], and go into Judaea, that thy disciples also may see the works that thou doest. For there is no man that doeth any thing in secret, and he himself seeketh to be known openly. If thou do these things, shew thyself to the world. For neither did his brethren believe in him. John 7:2-5 emphasis mine
When Jesus therefore saw his mother, and the disciple standing by, whom he loved, he saith unto his mother, Woman, behold thy son! Then saith he to the disciple, Behold thy mother! And from that hour that disciple took her unto his own home. John 19:26-27
Why did Jesus commit Mary into the care of the beloved disciple, not James, who is known as his brother?
This question seems to be more involved in interpretations concerning the the Sacred Texts of the Gospels rather than the opinions various denominations.
Almost all Christians are in accord that at the moment of Christ’s death, Joseph the husband of Mary was already dead!
James may have simply been a cousin of Jesus and not a real brother of Jesus as we understand the word brother to mean in English. Thus in the eye of suffering Saviour, he commended his mother to the Disciple he loved the Most and not James.
James the Just, or a variation of James, brother of the Lord (Latin: Iacomus from Hebrew: יעקב Ya'akov and Greek: Ἰάκωβος Iákōbos, can also be Anglicized as "Jacob"), was a brother of Jesus, according to the New Testament. He was an early leader of the Jerusalem Church of the Apostolic Age. He died as a martyr in AD 62 or 69.
Catholics and Eastern Orthodox, as well as some Anglicans and Lutherans, teach that James, along with others named in the New Testament as "brothers" of Jesus, were not the biological children of Mary, but were possibly cousins of Jesus, or half-brothers from a previous marriage of Joseph (as related in the Gospel of James).
Roman tradition holds that this James is to be identified with James, son of Alphaeus, and James the Less. It is agreed by most that he should not be confused with James, son of Zebedee.
Cousin, son of a sister of Mary
James, along with the others named "brothers" of Jesus, are said by others to have been Jesus' cousins. This is justified by the fact that cousins were also called "brothers" and "sisters" in Jesus' native language, Aramaic, which, like Biblical Hebrew, does not contain a word for cousin. Furthermore, the Greek words adelphos and adelphe were not restricted to the meaning of a literal brother or sister in the Bible, nor were their plurals. However, unlike some other New Testament authors, apostle Paul had a perfect command of Greek, a language which has a specific word for cousin and another for brother calling James "the brother of our Lord" (Galatians 1:19).
Eusebius of Caesarea (c. 275 – 339) reports the tradition that James the Just was the son of Joseph's brother Clopas and therefore was of the "brothers" (which he interprets as "cousin") of Jesus described in the New Testament.
This is echoed by Jerome (c. 342 – 419) in De Viris Illustribus (On Illustrious Men) – James is said to be the son of another Mary, wife of Clopas and the "sister" of Mary, the mother of Jesus – in the following manner:
James, who is called the brother of the Lord, surnamed the Just, the son of Joseph by another wife, as some think, but, as appears to me, the son of Mary, sister of the mother of our Lord of whom John makes mention in his book...
Jerome refers to the scene of the crucifixion in John 19:25, where three women named Mary – Mary, the mother of Jesus, Mary of Clopas, and Mary Magdalene – are said to be witnesses. John also mentions the "sister" of the mother of Jesus, often identified with Mary of Clopas due to grammar. Mary "of Clopas" is often interpreted as Mary, "wife of Clopas". Mary of Nazareth and Mary of Clopas also need not be literally sisters, in light of the usage of the said words in Greek, Hebrew and Aramaic.
Mary of Clopas is suggested to be the same as "Mary, the mother of James the younger and Joses", "Mary the mother of James and Joseph" and the "other Mary" in Jesus' crucifixion and post-resurrection accounts in the Synoptic Gospels. Proponents of this identification argue that the writers of the Synoptics would have called this Mary, simply, "the mother of Jesus" if she was indeed meant to be the mother of Jesus, given the importance of her son's crucifixion and resurrection: they also note that the mother of James and Joses is called "Maria", whereas the mother of Jesus is "Mariam" or "Marias" in Greek. These proponents find it unlikely that Mary would be referred to by her natural children other than Jesus at such a significant time (James happens to be the brother of one Joses, as spelled in Mark, or Joseph, as in Matthew).
Jerome's opinion suggests an identification of James the Just with the Apostle James, son of Alphaeus; Clopas and Alphaeus are thought to be different Greek renderings of the same Aramaic name Khalphai. Despite this, some biblical scholars tend to distinguish them; this is also not Catholic dogma, though a traditional teaching.
Since this Clopas is, according to Eusebius, Joseph of Nazareth's brother (see above) and this Mary is said to be Mary of Nazareth's sister, James could be related to Jesus by blood and law. - James, brother of Jesus