You may know this, but if you don't, here it is. Wonder Woman has a black sister. And her name is Nubia. I remember seeing her in the SuperFriends comic book (issue 25)
Wonder Woman tries to liberate the oppressed women of the African continent. But Diana is interrupted by, Nubia who is temporarily under the control of the evil Overlord. Nubia tells her to back off and they fight, eventually the Overlord is defeated and they are back as normal.
She's rarely featured again, until Phil Jimenz brought her back, but changed her origin completely. However, I liked the fact that in the 70s Nubia was created to bring black readers to the fold. I liked that she was Wonder Woman's sister. There are so many stories that could've been told through the eyes of the other warrior princess.