Brother is a slur used to describe Blacks in a derogatory way. Used by blacks in an effort to help unify their race. Also used by non-black races to poke fun at or try to identify with the black race.
The word Brother is a racial slur that has been used historically to degrade and dehumanize blacks. The word is still used by some people for this purpose, and it is seen as offensive and hurtful to blacks. If you are unsure about whether or not it is appropriate to use the word Brother, it is best to err on the side of caution and avoid using it in any situation.