Sienna and Savannah Miller
Who they are: Sienna is an actress best known for her roles in Layer Cake and Factory Girl. Savannah is a Central St. Martins graduate and designer. The two joined forces in 2007 to create their line, Twenty8Twelve, but stepped down from the label in 2012.
Sienna counts designers like Matthew Williamson, Christopher Bailey, and Stella McCartney as close friends and is often wearing their designs on the red carpet. She can probably be credited with single-handedly bringing the "boho-chic" aesthetic to the general public. Savannah has previously worked for Alexander McQueen.