Let's explore the relationship between Paul and James. First, calibrate your sarcasm detectors for Paul's attitude regarding circumcision.
Galatians 5:11-12 NIV
11 Brothers and sisters, if I am still preaching circumcision, why am I still being persecuted? In that case the offense of the cross has been abolished. 12 As for those agitators, I wish they would go the whole way and emasculate themselves!
Paul tells us that the people who were held in high esteem didn't mean anything to him, then names those pillars as James, Cephas, and John.
Galatians 2:6, 9 NIV
6 As for those who were held in high esteem--whatever they were makes no difference to me; God does not show favoritism--they added nothing to my message.
9 James, Cephas and John, those esteemed as pillars, gave me and Barnabas the right hand of fellowship when they recognized the grace given to me. They agreed that we should go to the Gentiles, and they to the circumcised.
Paul explicitly states that he opposed Cephas and points out that James had the human authority to send people (to whom Cephas kowtowed) to other places.
Galatians 2:11-12 NIV
11 When Cephas came to Antioch, I opposed him to his face, because he stood condemned. 12 For before certain men came from James, he used to eat with the Gentiles. But when they arrived, he began to draw back and separate himself from the Gentiles because he was afraid of those who belonged to the circumcision group.
The opening of Galatians is a pretty typical of Pauline and Deutero-Pauline letters except for the part about who did not send him. The Greek sources say, "not by men (plural form) and man (singular form)." Most translations make the singular form some kind of collective but that would be redundant following the plural form. I think the NIV gets it right by making it singular. Paul made it clear that he was not sent by someone like James.
Galatians 1:1 NIV
1 Paul, an apostle--sent not from men nor by a man, but by Jesus Christ and God the Father, who raised him from the dead--
Paul is sarcastically implying that James sends people on missions the way the Lord sends Paul on missions, as if James thinks he is at the Lord's level, by using human authority send people on missions.
Galatians 1:19 NIV
19 I saw none of the other apostles--only James, the Lord's brother.
Since Paul uses so much sarcasm toward James, why would we assume that is not more of the same?
In 1 Corinthians 9, someone seems to be questioning why the Corinthians are sending Paul a stipend for his work.
1 Corinthians 9:5 NIV
5 Don't we have the right to take a believing wife along with us, as do the other apostles and the Lord's brothers and Cephas?
Again, we find Paul calling people "brothers of the Lord" in conjunction with Paul denying he uses human authority while implying that others do.
1 Corinthians 9:8 NIV
8 Do I say this merely on human authority? Doesn't the Law say the same thing?
But then we cannot say that Paul isn't a hypocrite on that matter because he goes on to justify that he gets paid for his work by citing Deuteronomy 25:4 about not muzzling an ox while it treads grain but then uses his own human authority to say that the verse applies to people, not animals.
1 Corinthians 9:9-10 NIV
9 For it is written in the Law of Moses: "Do not muzzle an ox while it is treading out the grain." Is it about oxen that God is concerned? 10 Surely he says this for us, doesn't he? Yes, this was written for us, because whoever plows and threshes should be able to do so in the hope of sharing in the harvest.
Paul didn't think anybody was the Lord's brother. He was using sarcasm when he accused people of using human authority to do what Paul thought was the business of the Lord.