'Brother' in the Bible

Paul, an apostle of Jesus Christ by the will of God, and Timothy our brother, unto the church of God which is at Corinth, with all the saints which are in all Achaia:

I had no rest in my spirit, because I found not Titus my brother: but taking my leave of them, I went from thence into Macedonia.

And we have sent with him the brother, whose praise is in the gospel throughout all the churches;

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.

I desired Titus, and with him I sent a brother. Did Titus make a gain of you? walked we not in the same spirit? walked we not in the same steps?