[HarleyD]

Hi Cronos. The Greek word for brother is adelphos. This is used often in the sense of "directly related" brother, spiritual brother. brethren, etc. In the cases presented, brother is always used as a direct relative-not cousin. Paul uses another word (anepsios) for cousin in Col 4:10 when he states:

10 Aristarchus, my fellow prisoner, sends you his greetings; and also Barnabas’s cousin Mark (about whom you received instructions; if he comes to you, welcome him);

If, as you suppose, they referred to brothers as cousins and visa versa, then Paul would not have made this distinction. The Scripture use of this word clearly shows there was a distinction between "cousin" and "brother". If these were our Lord Jesus' "cousins", the correct Greek term would have been anepsios and not adelphoi.

BTW-I have checked all the Catholic arguments for this. The argument is normally, "Well, they can be used interchangably and adelphoi is a term of endearment." Of course this argument is toast when you get to some of the ways adelphoi is used in the scriptures (such as his brothers did not even believe Him). Not much endearment there. And then there doesn't seem much endearment of Paul sending greeting to Mark by using the term cousin (anepsio).

[Cronos]

Adelphi is used for cousins or close relatives in Deut. 23:7; Neh. 5:7; Jer. 34:9.

Lot, for example, is called Abraham’s “brother” (Gen. 14:14), even though, being the son of Haran, Abraham’s brother (Gen. 11:26–28), he was actually Abraham’s nephew. Similarly, Jacob is called the “brother” of his uncle Laban (Gen. 29:15). Kish and Eleazar were the sons of Mahli. Kish had sons of his own, but Eleazar had no sons, only daughters, who married their “brethren,” the sons of Kish. These “brethren” were really their cousins (1 Chr. 23:21–22).

The terms “brothers,” “brother,” and “sister” did not refer only to close relatives. Sometimes they meant kinsmen (Deut. 23:7; Neh. 5:7; Jer. 34:9), as in the reference to the forty-two “brethren” of King Azariah (2 Kgs. 10:13–14).

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Neither Hebrew nor Aramaic have a special word meaning “cousin,” speakers of those languages could use either the word for “brother” or a circumlocution, such as “the son of my uncle.” But circumlocutions are clumsy, so the Jews often used “brother.”

The writers of the New Testament were brought up using the Aramaic equivalent of “brothers” to mean both cousins and sons of the same father—plus other relatives and even non-relatives. When they wrote in Greek, they did the same thing the translators of the Septuagint did.

In the Septuagint the Hebrew word that includes both brothers and cousins was translated as adelphos, which in Greek usually has the narrow meaning that the English “brother” has. Unlike Hebrew or Aramaic, Greek has a separate word for cousin, anepsios, but the translators of the Septuagint used adelphos, even for true cousins.

This same usage was employed by the writers of the New Testament and passed into English translations of the Bible. To determine what “brethren” or “brother” or “sister” means in any one verse, we have to look at the context. When we do that, we see that insuperable problems arise if we assume that Mary had children other than Jesus.