(Proverbs 17:17 KJV) A friend loveth at all times, and a brother is born for adversity.
Notice that this is a parallel statement. One of the parallels is the similarities between “friend” (7453) and “brother” (251). Since this is the Old Testament we can take the term “brother” literally.
I believe there is a hierarchy in relationships. At the bottom you have all mankind. We are expected to love and be courteous to everyone. Honesty is not for an exclusive group. At the other extreme the general world would put blood relatives. Christians would put brethren in Christ above that. We owe more to fellow believers than we do to non-believing siblings. That does not let us off the hook but simply tries to remind us of what is expected.
So? We are to be different. We are also to be stewards of our time and treasure. Use them wisely with special attention to brothers and brethren.