second... The writings in the NT that talk of JEsus' brothers AND sisters was ORIGINALLY written in Greek and the Greek does have a word for cousin... if that is what the NT writers intent was (that these brothers and sisters where actual cousins) they would have written these words
female cousin = ξαδέλφη (ksaTHElfee - th like in the word the)
male cousin = ξάδελφος (KSAthelfos - th like in the word the)
cousins = ξαδέλφια (ksaTHElfia - th like in the word the)
As evidenced by other scriptures that are correctly translated from the original that means exactly what it says... cousin.
My fellow prisoner Aristarchus sends you his greetings, as does Mark, the
cousin of Barnabas. (You have received instructions about him; if he comes to you, welcome him.)
And, behold, thy cousin Elisabeth, she hath also conceived a son in her old age: and this is the sixth month with her, who was called barren.
(in Context) (Whole Chapter)
And her neighbours and her cousins heard how the Lord had shewed great mercy upon her; and they rejoiced with her.
The word Adolphos was NOT used. God knows what he is doing and what he wishes to reveal without ambiguity.