Were it not for the prevalence of the false doctrine of "the perpetual virginity of the blessed Virgin" this subject would hardly have seemed worthy of the long discussions which have been written about it. The expression in Matthew 1:25, "and knew her not till she had brought forth her first-born son; and he called his name Jesus," testifies not only to the fact of the virgin birth of our Lord, but also to the other items, well-known later, that she bore to Joseph several children while Jesus was growing up. Mark 6:3, "Is not this the carpenter, the son of Mary, the brother of James, and Joses, and of Juda and Simon? and are not his sisters here with us?" testifies that when Jesus was a little more than 30 years of age he had at least six uterine (from the same mother) brothers and sisters. If, as some have ingeniously (cunningly) argued, these had been sons of Joseph by a previous marriage, the whole argument of this passage would have lost its force.
John 7:1-10 states that the brothers of Jesus, in the midst of His ministry did not believe in Him, though it is almost a certainty that James was not only the human leader of the first church at Jerusalem by 50 AD (Acts 15:13, 21:18) but the writer of the epistle that bears his name; and that Jude, the author of the epistle, was the "Juda" of Mark 6:3.
In addition the following should be noted.
There are some who claim that the term "Brothers", in this and other verses, many times meant any other man in the village, or of any man in the world, as well as a natural blood related brother. And while this can be true, for it was also used this way, for the Greek word "adelphos" translated as "Brothers" has been used in this context as well as a blood related brother from the same mother or father.
But the Greek word " adelphe" translated as "sisters" was only used of a blood related woman who's mother or father was the same as theirs. It is only in much later times, and in other parts of the world that the word "sister" was applied to someone other than a blood relation.
Rev. Jack Barr