Step peppers refers to a white person's Black "step" relatives. The term step pepper can be used by white family members when speaking of a step-parent or a step-brother/sister who is Black. The term originated in 2011 during a broadcast of Eric's Awesome Show on Adult Swim (Cartoon network's late night programming schedule). It was used during a skit in which a funeral was being held, as the preacher addressed each of the relatives of the deceased.
White person 1 My dad married Sha'queentia and she gots four kids so now I gots 5 step peppers!
White person 2 I'm glad my mom's new husband Tyrone doesn't have any kids. I only have one. And he's not even a full pepper...he is only half-Black.
White person 1 Dag, yo! I be wishin' I be you!
White person 2 Well, at least you're learning Ebonics.