They have always been in vogue, but twin actresses and clothing designers Mary Kate and Ashley Olsen are now truly in Vogue, gracing the cover of the fashion magazine's newest best dressed issue.

The widely-read edition, which was unveiled on Thursday and hits newsstands on Nov 15, puts its spotlight on nine global sister acts from British royalty, the Duchess of Cambridge Kate Middleton and her sister Pippa, to celebrity singers Beyonce and Solange Knowles.

"It's been a year of sisters, most famously with Catherine and Pippa Middleton," Mark Holgate, Vogue Fashion News Director and Editor of the best dressed issue, told Reuters.

Holgate credits the Middletons with popularizing their own mid-thigh length of dress: "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 it was the Olsen twins, who rose to fame as child stars on US TV and as adults founded two successful high-end clothing labels, who were picked for the prestigious cover. Holgate called the choice: "kind of a no-brainer."

"Are there any more chic, stylish, cool, and original sisters than Mary Kate and Ashley Olsen? They are incredibly stylish," he said of the twins.

The issue also highlights sisters with contrasting styles, such as the Maras - actresses Rooney of the upcoming "The Girl with the Dragon Tattoo" and Kate, currently seen on TV's thriller series "American Horror Story."

The colorful Solange Knowles, younger sister of pop superstar Beyonce, is known for taking style risks including shaving her head, donning afro wigs and mixing prints and colors.

Read the full story here.

Click on the thumbnails for some of the stylist sisters that made Vogue magazine's best dressed list of 2011.