'Brethren' in the Bible

Brethren, a new command I write not to you, but an old command, that ye had from the beginning -- the old command is the word that ye heard from the beginning;

Do not wonder, my brethren, if the world doth hate you;

we -- we have known that we have passed out of the death to the life, because we love the brethren; he who is not loving the brother doth remain in the death.

in this we have known the love, because he for us his life did lay down, and we ought for the brethren the lives to lay down;