Strong's Concordance
http://biblehub.com/greek/80.htm
adelphos: a brother
Original Word: ἀδελφός, οῦ, ὁ
Part of Speech: Noun, Masculine
Transliteration: adelphos
Phonetic Spelling: (ad-el-fos')
Short Definition: a brother
Definition: a brother, member of the same religious community, especially a fellow-Christian.
Here is a link to the occurrences of the Greek word *adelphos*.
http://biblehub.com/greek/80.htm
The word *sister* (adelphe) in the Greek is the same.
http://biblehub.com/greek/79.htm
The word used is *brother* not *cousin*.
It can't mean a member of the same religious community in the context in which they occur, because then that would mean every man in Israel could be identified as Jesus' brother. So that would not identify Jesus as anyone in particular's brother.
It's not going to mean *brother in Christ* as that concept was not yet in place and the Jews, who knew Jesus as a Jew and knew His brothers as Jews, would not even begin to understand the new birth and what being in Christ meant.
They didn't even understand who JESUS was, much less being a *brother in Christ*.
The only definition left then, is to mean physical brother.
And it would not be *cousin*.
The word for *relative* that is used for Elizabeth is *suggenes*, not *adelphe*.
http://biblehub.com/greek/4773.htm
Strong's Concordance
suggenes: akin, a relative
Original Word: συγγενής, ές
Part of Speech: Adjective
Transliteration: suggenes
Phonetic Spelling: (soong-ghen-ace')
Short Definition: akin, a relative
Definition: akin to, related; subst: fellow countryman, kinsman.
Where the Holy Spirit inspires the authors to get specific about actual maternal offspring as in "son of Mary," only one person is named as such: Jesus Christ.
Granted, there is a verse where Scripture defines what is meant by Jesus' brethren, as in, specifically, Mary's other offspring. It's meant, I think, to include even you and me.
Tagline.