It's not the doctrine being supported. It's simple Greek. This is the words used:
ἀδελφός. It means .....well google translate it and you'll see it means something completely different in modern greek but it means in the Greek used:# 80 Greek in the Strongs
1) a brother, whether born of the same two parents or only of the same father or mother
2) having the same national ancestor, belonging to the same people, or countryman
3) any fellow or man
4) a fellow believer, united to another by the bond of affection
5) an associate in employment or office
6) brethren in Christ
a) his brothers by blood
b) all men
c) apostles
d) Christians, as those who are exalted to the same heavenly place
Nope, I wasn't trying to show my doctrine but showing what it can mean. Now if you google translate it it means "sister"
The NT context is clear and all connections of the Scriptures defining his relations and other relations are of a piece.
The Word is clear when dealing with intimate family relationships that there were brothers -not cousins- called by Jesus to be His disciples, and His 1st cousin once removed, John, was his forerunner -a kinsman- but they did not have a close relationship.
Jesus was esp concerned to appear to His womb brothers who did not believe in Him as Messiah until after His resurrection.
Jesus was the elder brother who had the inheritance of the throne of David, being Joseph's legal firstborn heir. If Joseph had any sons before Jesus was born, then the firstborn of them would inherit the throne of David through Joseph....the genealogies are given of Joseph through his natural father, Jacob, and his legal father, Heli, who died before his wife bore him children, so Jacob married her and they had Joseph, by law the son of Heli who received Heli's name and inheritance and through whom he passed the inheritance of the throne of David to Jesus, his legal son.
Mark was the nephew of Barnabas and Barnabas was the brother of Mark's mother.
James and John -brothers of one father
Jude and James Simon and Jesus -brothers of one womb, with James and John being brothers of one father and one mother
Andrew and Peter -brothers of one father who is named.
Mary, Martha were sisters and Lazarus was their brother.
Jesus had brothers and sisters younger than he, at least 6 of them.
His brothers and sisters were the children of Joseph, and of Mary:
Mar 6:3 Is not this the carpenter, the son of Mary, the brother of James, and Joses, and of Juda, and Simon? and are not his sisters here with us? And they were offended at him.
Mat 12:46
While he yet talked to the people, behold, [his]
mother and his brethren stood without, desiring to speak with him.
Jesus' brothers did not believe in Him until after the resurrection:
John 7:7 After these things Jesus was walking in Galilee, for He was unwilling to walk in Judea because the Jews were seeking to kill Him. 2 Now the feast of the Jews, the Feast of Booths, was near.
3 Therefore His brothers said to Him, “Leave here and go into Judea, so that Your disciples also may see Your works which You are doing. 4 For no one does anything in secret [a]when he himself seeks to be known publicly. If You do these things, show Yourself to the world.” 5 For not even His brothers were believing in Him. 6 So Jesus *said to them, “My time is not yet here, but your time is always opportune. 7 The world cannot hate you, but it hates Me because I testify of it, that its deeds are evil. 8 Go up to the feast yourselves; I do not go up to this feast because My time has not yet fully come.” 9 Having said these things to them, He stayed in Galilee.
1
0 But when His brothers had gone up to the feast, then He Himself also went up, not publicly, but as if, in secret.
Mat 4:21 And going on from thence,
he saw other two brethren, James [the son] of Zebedee, and John his brother, in a ship with Zebedee their father, mending their nets; and he called them.
Mat 4:18
And Jesus, walking by the sea of Galilee,
saw two brethren, Simon called Peter, and Andrew his brother, casting a net into the sea: for they were fishers.
Jhn 11:19 And many of the Jews came to Martha and Mary, to comfort them concerning their brother.
Col 4:10 Aristarchus my fellowprisoner saluteth you, and
Marcus, sister's son to Barnabas, (touching whom ye received commandments: if he come unto you, receive him