In Acts 1:13And when they were come in, they went up into an upper room, where abode both Peter, and James, and John, and Andrew, Philip, and Thomas, Bartholomew, and Matthew, James the son of Alphaeus, and Simon Zelotes, and Judas the brother of James.
See All..., Judas is referred to as the brother of James in the KJV, yet in all of the newer versions, he is called the son of James. Do you know why all of the newer versions change this?

Thank you for pointing out this distinction and for giving some good examples. I think you would find the same thing in Luke 6:16And Judas the brother of James, and Judas Iscariot, which also was the traitor.
See All..., which in the King James Bible states, "And Judas the brother of James, and Judas Iscariot, which also was the traitor."

I have pointed out in other places that every difference between the King James Bible and modern versions cannot be attributed to a difference in the text used to translate the Bible. This is one of those examples. There is no textual controversy or variant reading involved in the Greek manuscripts. That is, all translators seem to agree on the reading of the Greek phrase in question in these verses. The difference is solely a choice of translation.

Now, I will say something that could be misunderstood but I believe it needs to be said: the Greek phrase can be honestly translated either way. You see, the Greek phrase that is translated either "Judas the brother of James" or "Judas the son of James" comes from only two words in the Greek. The first is Judas and second is James. The declension of the nouns clearly shows the phrase to mean, "Judas of James." That means that the relationship is a close one and that Judas is related to James in a close family kinship. Therefore, Judas is almost certainly either a brother of James or a son of James. However, the phrase in and of itself does not make that distinction. In fact, the King James Bible indicates this uncertainty by putting "brother of" in italics both in Luke 6:16And Judas the brother of James, and Judas Iscariot, which also was the traitor.
See All... and in Acts 1:13And when they were come in, they went up into an upper room, where abode both Peter, and James, and John, and Andrew, Philip, and Thomas, Bartholomew, and Matthew, James the son of Alphaeus, and Simon Zelotes, and Judas the brother of James.
See All.... This means that there is no corresponding word in Greek to match the words "the brother."

Modern scholarship has decided that the relationship between Judas and James must be one of father and son and I am sure that they have their arguments for this choice. Yet, the footnotes of the various versions often admit that the phrase could refer to a brother to brother kinship. Therefore, the choice to unanimously (as far as I can tell) change the acceptable reading of the King James must have some motivation. Let us explore some possibilities.

1. Modern scholarship is better and has the answer absolutely determined. Is this right? Probably not. Else, why do the notes still admit the possibility that the King James Bible is correct. The truth is, scholarship has not answered the question.
2. Modern scholars all copycat one another and this is the reading presently in vogue. This answer probably comes closer to the truth. Anyone who has compared many English versions has seen this copycat tendency over and over again. There is nothing worse than being scorned by the very scholars who are needed to puff you up.
3. We need some reason for denying that the author of the epistle of Jude was one of the apostles. This is certainly a motivation. In some of my reading I found that the modern reading was used to reject the possibility that the author of Jude was the apostle of Christ. The epistle in question begins, "Jude, the servant of Jesus Christ, and brother of James" in Jude 1:1Jude, the servant of Jesus Christ, and brother of James, to them that are sanctified by God the Father, and preserved in Jesus Christ, and called:
   See All.... Jude is simply another form of Judas. Traditional and popular teaching makes the author of Jude a half-brother of Jesus Christ. If one of the apostles was a Judas (Jude) who was the brother of James and Jude (of the epistle) was the brother of James, then they might very well be the same people. However, if the apostle was the son of James, the two were probably not the same.

In fact, most teachers believe that both Jude and James (of the book of James) were half-brothers of Jesus. And, it is true that Jesus had a half-brother named James and another named Judas (see Matthew 13:55Is not this the carpenter's son? is not his mother called Mary? and his brethren, James, and Joses, and Simon, and Judas?
See All...). But perhaps people want to give too much emphasis to the flesh here and desire to elevate the physical kinship of the men to Jesus. It is also very possible that all of the New Testament epistles (Romans through Jude) were written by the twelve apostles and Paul, who was the apostle to the Gentiles (Romans 11:13For I speak to you Gentiles, inasmuch as I am the apostle of the Gentiles, I magnify mine office:
See All...). That would keep the teaching of New Testament scriptures in the hands of the chosen apostles. Perhaps modern scholars want too much to spread the authorship of the New Testament or perhaps they want to elevate the physical relationship and give too much credit to it. I am sure this could be further studied by others but I do not have the time right now to do it myself.

Of course, I must tell you this. Through a time of great study and a time of seeking, I came to trust in the providential working of God in the translation of the King James Bible. I have no problem accepting it as God's perfectly preserved word. I can easily admit that the text can honestly be translated either way and still believe with confidence that it is correct in the King James Bible. This is the Bible that God has put His stamp of approval on. I have no reason to doubt it.