While Kim Kardashian may arguably be the most famous sister, she may want to keep up with her younger sister- Kylie Jenner - who is definitely the richest... In Forbes annual ranking of America's Richest Self-Made Women, out in August, Jenner - is said to be worth about $900 million! She's the youngest person on the list and another year of growth will make her the youngest self-made billionaire ever, male or female, trumping Facebook CEO Mark Zuckerberg, who became a billionaire at 23.