The former childhood stars beat out Beyonce and her singer sister Solange Knowles for the honour.
Defending the publication's choice, Vogue executive Mark Holgate tells Reuters, "Are there any more chic, stylish, cool, and original sisters than Mary Kate and Ashley Olsen? They are incredibly stylish... Look at what they've done with (their fashion labels) The Row and Elizabeth and James. They are legitimate fashion forces."
Also making the exclusive list were acting duo Dakota and Elle Fanning, British royal Catherine, the Duchess of Cambridge and her sister Pippa Middleton, and The Social Network star Rooney Mara and her actress sister Kate.