Ashey and Mary-Kate Olsen aren't even 30, and yet they might be the richest and the most famous twins in the world. The girls started their careers by playing Michelle on Full House at the tender age of six months. They continued acting throughout their teens but eventually left the industry behind and started their own fashion line, The Row. In 2007, the Olsen twins were named the 11th richest women in the world.

Update: Thank you to our readers who pointed out that while these two look nearly identical, they are actually fraternal twins.