Charles Barkley to Derek Fisher and Matt Barnes -- 'Brothers Shouldn't Be Fightin' Brothers'

Charles Barkley pays no mind to the bro code ... he's visibly disappointed at Matt Barnes and Derek Fisher for their physical blow up.

TMZ Sports got Charles outside the London in NYC Saturday, and former NBA star made it clear ... it's irrelevant what Derek may or may have been been doing with Matt's estranged wife Gloria Govan ... "Brothers should not be fighting brothers."