'Brother' in the Bible

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

To the rest I say -- I, not the Lord -- if a brother has a wife who is not a believer and she is happy to live with him, he should not divorce her.

But if the unbeliever wants a divorce, let it take place. In these circumstances the brother or sister is not bound. God has called you in peace.

So by your knowledge the weak brother or sister, for whom Christ died, is destroyed.

For this reason, if food causes my brother or sister to sin, I will never eat meat again, so that I may not cause one of them to sin.

With regard to our brother Apollos: I strongly encouraged him to visit you with the other brothers, but it was simply not his intention to come now. He will come when he has the opportunity.