Galatians 1:19 "But other of the apostles saw I none, save James the Lord's brother". if one use the word G80 ἀδελφός adelphos (a-d̮el-fos') as (of faith) a brother in our Lord, Jesus), in this case it would be of no used. for the verse qualified it's use, by saying "the Lord's brother" and not "our brother" (as in the Faith). for I'm sure that the apostles also at Jerusalem was Paul's "brothers" in the Faith. but here in this verse he used the "Lord's Brother. in 2 Corinthians 8:22 we see the use of (in the faith as brothers clearly). "And we have sent with them our brother, whom we have oftentimes proved diligent in many things, but now much more diligent, upon the great confidence which I have in you". here this is how G80 ἀδελφός adelphos (a-d̮el-fos') as (of faith) a brother in our Lord, Jesus).
but in direct relation to only his kin in flesh we see it not use as in the FAITH. . scripture, Mark 6:1-6 "And he went out from thence, and came into his own country; and his disciples follow him. (TAKE NOTE OF THIS). And when the sabbath day was come, he began to teach in the synagogue: and many hearing him were astonished, saying, From whence hath this man these things? and what wisdom is this which is given unto him, that even such mighty works are wrought by his hands? 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. But Jesus said unto them, A prophet is not without honour, but in his own country, and among his own kin, and in his own house. And he could there do no mighty work, save that he laid his hands upon a few sick folk, and healed them. And he marvelled because of their unbelief. And he went round about the villages, teaching".
now, if James, and Joses, and of Juda, and Simon was his brothers in the faith why not mention by separate name also the other 9 disciples as his brothers in faith, since they was with him, if one use G80 ἀδελφός. adelphos here in this scripture as "brothers" in the faith.
Peace in Christ Jesus, Yeshua.