It's all about being real and true to yourself. The opposite of real is fake.
You don't have to be black to be a real nigga, but it helps.
Being a real nigga is doing what ever you do, doing it best, not pretending to be a wannabe thug like everybody else.
Bruce Lee is a real nigga.
Chuck norris is a real nigga.
Most rappers(e.g. lil flip,g-unit,D4l, gille da kid) ain't