Sibling rivalry has been around since the dawn of time – especially with sisters – but nothing could be further from the truth with designer-duo Sienna and Savannah Miller, they simply love working together.

After setting up their eponymous label Twenty8Twelve just over five years ago, the girls have experienced massive success with their effortlessly chic style in the fashion world – and couldn’t be happier with their joint business venture.

“This business means we get to see more of each other and work on something we both enjoy,” says Sienna.

“There’s never been any conflict,” adds Savannah. “We work really well together, plus it means we have to see each other two nights a week so it’s a great excuse to say to my husband, ‘You have to take the kids, I’m working with my sister’!”

Now with their eleventh collection under their fashionable belts, the stylish siblings feel happy and confident they’ve found their niche with the AW11 collection.

“I feel like we’ve been finding our niche,” Savannah said. “Maybe we’ve tried to be a bit too avant garde in the past, but now we do that with print and texture and just focus on making wearable clothes we’d love to wear. We have an amazing team of seven unsung heroes who work with us – they really understand us and where we want the brand to be – and we’re getting there.”

The brand new AW11 collection also poses as the highest quality line to date.

“We’ve moved all our tailoring to London as well,” said Sienna to Vogue UK, “which has made a massive difference in terms of quality and fit – and working with a pattern cutter here feels right for the brand too. We also now get each sample in both our sizes which has made a huge difference to the way we make changes. I’ve had the great fortune to wear a lot of beautiful designer clothes, and you know when something feels right.”

The Twenty8Twelve spring/summer 2011 collection is now available from Selfridges.