What does the Bible say about being one of the brethren?

In Ephesians 6:23-24, the Apostle Paul explicitly states, 'Peace be to the brethren, and love with faith from God the Father and the Lord Jesus Christ. Grace be with all them that love our Lord Jesus Christ in sincerity.' This scripture clarifies that the promises and gifts from God are directed specifically to those known as the brethren. It emphasizes the importance of a sincere love for Christ as the defining characteristic of being part of this spiritual family, which has ramifications for one's eternal standing.