Word: brethren in 1 John

Brethren, I write no new commandment unto you, but an old commandment which ye had from the beginning. The old commandment is the word which ye have heard from the beginning.

1 John 3:13

Marvel not, my brethren, if the world hate you.

1 John 3:14

We know that we have passed from death unto life, because we love the brethren. He that loveth not his brother abideth in death.

1 John 3:16

Hereby perceive we the love of God, because he laid down his life for us: and we ought to lay down our lives for the brethren.