Designers and sisters Savannah Miller (left) and Sienna Miller during a rehearsal for their Twenty8Twelve spring/summer London Fashion Week show, at the Old Sorting Office in central London Stock Photo - Alamy

Celebrity sisters Sienna and Savannah Miller pose for their portrait at the launch of their fashion label's latest collection: Twenty8Twelve. London F Stock Photo - Alamy

Sienna and Savannah Miller launch their new Spring Summer 2011 Twenty8Twelve collection at Selfridges in London Stock Photo - Alamy

Sienna and savannah miller hi-res stock photography and images - Alamy

Sienna Miller: Twenty8Twelve at London Fashion Week!: Photo 2239912, Savannah Miller, Sienna Miller Photos

Sienna and Savannah Miller design catwalk show - The San Diego Union-Tribune

She Is Inherently Golden”: Savannah Miller On Her Sister Sienna Miller's Style

Nervous Sienna Miller makes London Fashion Week debut as her THREE mums turn up for support

Sienna and Savannah Miller design catwalk show - The San Diego Union-Tribune

Sienna Miller so excited about LFW, British Vogue

Sienna and savannah miller hi-res stock photography and images - Alamy

Sienna and Savannah Miller design catwalk show - The San Diego Union-Tribune

Sienna and Savannah Miller design catwalk show - The San Diego Union-Tribune

Savannah miller and sienna miller hi-res stock photography and images - Alamy

British actress/designer Sienna Miller and designer Savannah Miller attend Twenty8Twelve Spring/Summer catwalk show at Fashion Week in London on September 18, 2010. UPI/Rune Hellestad Stock Photo - Alamy

Designers and sisters Savannah Miller (left) and Sienna Miller during a rehearsal for their Twenty8Twelve spring/summer London Fashion Week show, at the Old Sorting Office in central London Stock Photo - Alamy