25. Ashley & Mary-Kate Olsen
40u40 main mary kate ashley olsen
Mary-Kate (left) and Ashley Olsen (right)
Age: 26

Co-CEOs, Dualstar Entertainment Group

The two sisters like to get a headstart. They had their acting debut as 6-month-olds and launched their first fashion line when they were 12. Nowadays they're focused on running their fashion empire, which has grown into one of Seventh Avenue's hottest collections. Their company is home to their three core fashion lines: luxury The Row, contemporary Elizabeth and James, and mass-market Olsenboye, which is sold in partnership with J.C. Penney. The casual clothing and T-shirt ecommerce brand Stylemint round out the portfolio. Capping off a rise that has stunned even the most hardened fashion observers, the twins recently walked away with the most coveted award at the Council of Fashion Designers of America, Womenswear Designer of the Year -- fashion's equivalent of winning Best Picture at the Oscars.

Baggy: An alligator backpack from The Row reportedly sold out despite its $39,000 price tag.

--Caitlin Keating


@FortuneMagazine - Last updated October 17 2012 05:11 PM ET
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