'Brother' in the Bible

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

But actually, I wrote to you not to associate with any so-called brother if he is an immoral person, or covetous, or an idolater, or a reviler, or a drunkard, or a swindler—not even to eat with such a one.

but brother goes to law with brother, and that before unbelievers?

But to the rest I say, not the Lord, that if any brother has a wife who is an unbeliever, and she consents to live with him, he must not divorce her.

Yet if the unbelieving one leaves, let him leave; the brother or the sister is not under bondage in such cases, but God has called us to peace.

For through your knowledge he who is weak is ruined, the brother for whose sake Christ died.

Therefore, if food causes my brother to stumble, I will never eat meat again, so that I will not cause my brother to stumble.

But concerning Apollos our brother, I encouraged him greatly to come to you with the brethren; and it was not at all his desire to come now, but he will come when he has opportunity.