Is this normal?

Is it normal for my two and a half year old son to hit and punch and bite his mom and dad and little brother when mad? Hes been doing it for close to a year already...it doesn't matter what we do or say, he will not stop! I'm at my wits end with it. We've put him in time outs, spanked him (not hard just enough to catch his attention, tried explaining that hands are not for hitting and that biting and kicking is wrong and hurts, but it doesnt matter, he talks back and gives attitude and just continues to do it. I dont know why this is happening, but I dont know what else to do anymore....