Sienna Miller and her sister Savannah "couldn't be closer'.

The siblings run their own fashion label Twenty8Twelve together and the pair are so close Savannah reveals she only feels "whole" when she's with her sister, much to her husband's dissatisfaction.

Savannah said: ""We really are like each other's other half. I feel as though I'm whole when I'm with her, which sounds ridiculous - my husband would be livid - but we create something that's complete. We literally..."

Sienna added: "Complete each other's sentences! People always want to hear about some sort of catfight but we couldn't be closer."

While Sienna has become famous for her acting career, Savannah says she was never jealous of her sister because she always wanted to be "in the background".

She explained to Australia's Herald Sun newspaper: "Sienna's always been the one who wanted to do plays. And I've always wanted to be in the background, designing clothes. People ask me if I'm jealous, but it's never entered my head.

"Sienna entertained me my entire childhood; she's the funniest person I've ever met."