'Brethren' in the Bible

I will declare thy name unto my brethren, in the midst of the congregation will I praise thee.

I am become a stranger unto my brethren, and an alien unto my mother's sons;

For my brethren and companions' sakes I will say, Peace be within thee!

{A Song of degrees. Of David.} Behold, how good and how pleasant it is for brethren to dwell together in unity!