Mary-Kate and Ashley Olsen have been named among the world's best dressed women, by US Vogue. The designer siblings grace the cover of this month's best dressed supplement, which pays tribute to their style as well as other famous sisters, including Duchess Catherine and Pippa Middleton, Beyonce and Solange Knowles and Dakota and Elle Fanning.

"It's been a year of sisters, most famously with Catherine and Pippa Middleton. Their style is short enough to be impossible for an older-generation royal to wear, long enough to be decent when sitting or bending down to talk to a child. But are there any more chic, stylish, cool, and original sisters than Mary Kate and Ashley Olsen? They are incredibly stylish," said Mark Holgate, Vogue Fashion News Director and Editor of the Best Dressed issue.

"I feel like Mary-Kate's constantly evolving. What she does is when she finds a proportion or a silhouette or a specific outfit, she'll wear it until she's over it - which could be a week or it could be a year," Ashley said of her sister's style.

Mary-Kate added about Ashley, "There's always sort of a sense of a bohemian vibe. She's quirky, modern, bohemian."