Kylie Jenner has been named the youngest self-made billionaire of all-time, thanks to the booming cosmetics company she founded just three years ago.The 21-year-old, who is the half-sister of reality television stars Kim, Khloe and Kourtney Kardashian, has made it onto the annual Forbes list of billionaires.She has a net worth of $1bn (£759m).Facebook founder Mark Zuckerberg was 23 when he made onto the billionaire's list.