A simple responce to your Question.
Yes the New Testament was written in Greek.
And the Greek word kinsmen means: of the same kin, akin to, related by blood
in a wider sense, of the same nation, a fellow countryman
It doesnt necessarily mean Brother or whatever you are implying.
KJV (12) - cousin, 2; kin, 1; kinsfolk, 2; kinsman, 7;
NAS (11) - kinsman, 1; kinsmen, 3; relative, 1; relatives, 6;
A cousin is a relative.
Verse Display - Strong's Number: 4773
Original Word Transliterated Word
suggenh/v Suggenes
Translated Words
cousin, kin, kinsfolk, kinsman
The KJV Strong's Version - 5 Verses
Lu 1:36 -
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.
Also translated as Kinsmen, you have showed me yet again no evidence to suggest Mary had other Siblings.
Remember, Jesus was always referred to as "the" son of Mary, not "a" son of Mary.
Peace