Matthew 13:55-56 states, "Is not this the carpenter's son? is not his mother called Mary? and his brethren, James, and Joses, and Simon, and Judas? And his sisters, are they not all with us? Whence then hath this man all these things?"
As you pointed out, there are four named brothers and some unnamed and uncounted sisters, though the plural use of sisters shows that there must have at least two. The only brother we know anything significant about is James. He is called "the Lord's brother" in Galatians 1:19. Paul goes on to refer to this James as a pillar in the church of Jerusalem (Galatians 2:9). Certainly, he is the James who had great preeminence in the church of Jerusalem as mentioned in Acts 12:17; 15:13; 21:18. There is a good possibility that he was the author of the book of James, but this is in dispute by Bible students.
Now if the James who wrote the book of James was the brother of Jesus, then the author of the book of Jude may be the "Judas" of Matthew 13:55. The human author of Jude introduced himself as the "brother of James" (Jude 1:1). Another brief reference to the brothers of Jesus is when His brethren are named as some of those in the upper room in Acts 1:14. This is despite the fact that they did not believe in Christ during His earthly ministry (see John 7:5). I know of no other references to the brothers or sisters of Christ after His death and resurrection.
