How do you define a Christian or a brother in Christ? How do you define a Christian? How do you define what kind of person is your brother in Christ and what kind of person is not?
1 Corinthians 5:11  But now I have written unto you not to keep
  company, if any man that is called a brother be a fornicator, or
  covetous, or an idolater, or a railer, or a drunkard, or an
  extortioner; with such an one no not to eat.


If someone professes faith in Christ AND is aligning their behavior with the Bible, they are my brother. As the verse indicates, they have to both be called a Christian and behave like one.