Of course the entire world knows by now that the Williams sisters are the ultimate in sister goals. Serena is a 22-time Grand Slam winner and has her own clothing collection with HSN. Meanwhile, Venus is a world-ranked player herself, with four Olympic gold medals. (Ya know, just four. No big deal.) But long before they were household names and slaying all the record books, the pair were just two rising tennis stars trying to make a name for themselves in the game. In honor of the kickoff of the summer 2016 Olympics, Serena shared this adorable throwback pic of she and her sis. YES, that's their very first gold medal — from 16 years ago!