'Brother' in the Bible

Paul, called as an apostle of Christ Jesus by God’s will, and Sosthenes our brother:

But now I am writing you not to associate with anyone who claims to be a believer who is sexually immoral or greedy, an idolater or verbally abusive, a drunkard or a swindler. Do not even eat with such a person.

Instead, believer goes to court against believer, and that before unbelievers!

But I (not the Lord) say to the rest: If any brother has an unbelieving wife and she is willing to live with him, he must not leave her.

But if the unbeliever leaves, let him leave. A brother or a sister is not bound in such cases. God has called you to live in peace.

Then the weak person, the brother for whom Christ died, is ruined by your knowledge.

Therefore, if food causes my brother to fall, I will never again eat meat, so that I won’t cause my brother to fall.

About our brother Apollos: I strongly urged him to come to you with the brothers, but he was not at all willing to come now. However, he will come when he has an opportunity.