ANSWER: First of all we must understand that the authors of the Gospels were Jews. Even in the Old Testament there are instances where the word "adelphos" is used for the word "cousin", "close relative", or "kinsman" let's see where this is used in the Old Testament.
"eipen de abram tō lōt mē estō machē ana meson emou kai sou kai ana meson tōn poimenōn mou kai ana meson tōn poimenōn sou oti anthrōpoi adelphoi ēmeis esmen" ~Genesis 13:8, Greek Septuagint-Transliterated
|Parting of Lot and Abraham, 430 A.D. |
Sta. Maria Maggiore, Rome
Another verse where the English translation uses "cousin" (adelphou) is Jeremiah 32:12, "kai edōka auto tō barouch uiō nēriou uiou maasaiou kat' ophthalmous anameēl uiou adelphou patros mou kai kat' ophthalmous tōn estēkotōn kai graphontōn en tō bibliō tēs ktēseōs kai kat' ophthalmous tōn ioudaiōn tōn en tē aulē tēs phulakēs" ("and I gave this deed to Baruch son of Neriah, the son of Mahseiah, in the presence of my cousin Hanamel and of the witnesses who had signed the deed and of all the Jews sitting in the courtyard of the guard." ~New International Version).
|St. James the Lesser, El Greco|
Take note that this James who Paul speaks of is both called a "brother of the Lord" and an "apostle." If we read the list of the 12 Apostles we read that there are two James. The first James is called a "son of Zebedee." He would not be the James mentioned in Acts 12:1-2 for he was martyred early on. Even if it was him, his father was Zebedee, not Joseph.
St. Paul must have referred to the second James, who was an apostle (Luke 6:15-16). This James has a father named Alphaeus, not Joseph. Thus, James the apostle and Jesus were not uterine brothers. Easy enough. Some will argue, however, that this "James" was not an apostle or that he was not one of the original 12. Though this is a possibility—others in the New Testament, such as Barnabas in Acts 14, are referred to as "apostles" in a lesser sense—the argument from Scripture is weak. When Paul wrote about going "up to Jerusalem" to see Peter, he was writing about an event that occurred many years earlier, shortly after he had converted. He was basically going up to the apostles to receive approval lest he "should be running or had run in vain." It would be more likely he would have here been speaking about "apostles" (proper), or "the twelve." Christ calls the Apostles as "my brothers" in Matthew 20:10 and John 20:17:
|St. James the Greater, El Greco|
legei autē o iēsous mē mou aptou oupō gar anabebēka pros ton patera mou poreuou de pros tous adelphous mou kai eipe autois anabainō pros ton patera mou kai patera umōn kai theon mou kai theon umōn ("Jesus said, 'Do not hold on to me, for I have not yet ascended to the Father. Go instead to my brothers and tell them, 'I am ascending to my Father and your Father, to my God and your God.'" ~John 20:17, New International Version).
And according to the Bible Dictionary:
"Brother - Other familial relationships are also described by ah, Abraham and Lot, uncle and nephew, are referred to as brothers."(Mounces Complete Expository Dictionary of Old & New Testament Words, page 86)