'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 children.

For my brethren and companions' sakes, I will now 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!