One of the benefits of having a sister is the opportunity to raid her wardrobe from time to time, but when that sister is the future Queen consort, the stakes are raised. How exactly do you compete? Well, in the case of the Duchess of Cambridge and Pippa Middleton, the sharing does seem to go both ways. While Kate's classic style has given Pippa the chance to play dress-up in Alexander McQueen and probably turned her on to Issa and Hobbs, we're pretty sure Kate's forays into Project D and Matthew Williamson have something to do with her little sister's style advice. We're taking a look at a few of the British labels that these stylish sisters love. We all know both girls love L.K. Bennett shoes, but what about these other shared fashion favourites?
The label: After the tragic death of Lee Alexander McQueen in 2010, Sarah Burton took the helm of the beloved British label. She has been a favourite of the Duchess of Cambridge throughout her time in the public eye, creating custom outfits and adapting ready-to-wear styles to ensure they're modern but appropriate.
The outfits: Obviously, the most famous McQueen looks sported by the Middleton sisters were worn on Kate's wedding  day, when both the highly anticipated wedding dress and Pippa's bridesmaid dress were McQueen creations. The Duchess of Cambridge often wears McQueen dresses for high-profile engagements, including the Queen's Diamond Jubilee celebrations.
The label: Alice Temperley's eponymous label launched in 2000 and is a favourite of both Pippa and Kate. Trademarks include art deco details, intricate lace, and a strong focus on luxury fabrics. The designer often takes inspiration from the '20s, '30s, and '70s.
The outfits: Pippa is a particularly big Temperley enthusiast, having sat on the front row at the brand's London Fashion Week show. She's worn many dresses and separates from the label for events and nights out. Kate has chosen Temperley for public engagements and events and also wore a maxi dress from the Alice by Temperley diffusion label when she visited Polynesia.
The label: She may now choose to show on the New York Fashion Week calendar, but Jenny Packham's label has its roots in London. Specialising in bridal and formalwear, Packham's look is romantic, feminine, and often inspired by the 1930s.
The outfits: The Duchess of Cambridge has become a fully paid-up member of the Jenny Packham fan club in the last few years. Her teal-green lace-backed gown remains one of her best fashion moments, but she looks just as beautiful in the huge collection of Packham tea dresses that she's worn for daytime engagements. She's also no stranger to the label's sequinned dresses, having worn both pink and silver sparkly gowns in the past.
The label: Wickstead herself may have been born in New Zealand, but her London-based label has a very British feel. Pastel colours, chic tailoring, and ladylike elements feature heavily, but there's always the odd surprise as well.
The outfits: The Duchess of Cambridge quickly latched on to Wickstead's knee-length dresses in pastel shades and even wore the designer through her pregnancy. She also turned heads in a green dress coat from the designer. Pippa, meanwhile, looked to the darker side of the label when she wore a lacy black evening gown in late 2013.
The label: Lady Natasha Rufus Isaacs and Lavinia Brennan founded Beulah London in 2011 with the aim of doing good whilst dressing their friends in London society. Items carrying the Beulah butterfly logo have either been made by women who have been trafficked or been produced specifically to raise awareness or funds for its victims.
The outfits: The Duchess of Cambridge is a fan of Beulah's long-sleeved dresses, either midi or full length, which offer just the right amount of drama whilst remaining reserved enough for public engagements. Pippa opts for the label's more formfitting designs, including a bold purple satin dress she wore for her book launch.
The label: Orla Kiely's designs put a quirky spin on British classics, with plenty of pretty prints and '60s-inspired touches. She's particularly good at warm-weather clothing, knitwear, and long-sleeved dresses and is also known for her printed oilcloth handbags and accessories.
The outfits: The Duchess of Cambridge often picks Kiely's long-sleeved Winter dresses for days when she's on royal duty. A brown coat dress is a favourite, and she's also been spotted in a grey pleated dress and a navy pleated skirt. Pippa is a fan of the knitwear and has worn various Kiely cardigans. Even mum Carol has got in on the act, opting for an Orla Kiely dress on the day she visited Prince George after his birth.
The label: Established in 1997, Matthew Williamson is known for his bohemian touches, jewel colours, and Ibiza party style. Over the years, the look has grown up with the designer, but the embellishment and sense of adventure remains.
The outfits: Pippa is the big Williamson fan, picking his dresses for London parties and, in the case of one coral shift dress, Summer weddings. The jewelled embellishment and bold colours are probably a bit much for Kate's usual classic style, but even she was tempted once, wearing a grey peplum dress with a green stone trim for a film premiere.
Project D London
The label: A collaboration between designer Tabitha Somerset Webb and Dannii Minogue, Project D focussed on wearable, pretty dresses, feminine prints, and flattering shapes. Dannii left the label in 2013, and Webb has since focussed her efforts onto her own label, also a favourite of Pippa's.
The outfits: Pippa is the big Project D fan, wearing the brand's midlength printed dresses for weddings and trips to Wimbledon. She also chose a full-length gown for a charity gala. Kate opted for her little sister's label of choice when she visited Oceania, choosing a tropical floral shirt dress for her last day in Tuvalu.
The label: High-end high street store Whistles is known for effortless style at affordable prices, making it perfect for Kate's daytime engagements. It's particularly good for outerwear, simple silk dresses, high-quality fabrics, and great separates.
The outfits: Whilst Pippa favours the label's separates, the Duchess of Cambridge prefers to look to Whistles for knee-length dresses with waist detail, pleated skirts, and longer sleeve lengths. Both sisters own (or did they share?) a zip-up beige jacket.
The label: Like Whistles, Hobbs sits at the high end of the UK high street, with key items like coats and smart day dresses appealing to Kate's classic style. The younger line NW3 is better suited to Pippa's more experimental style.
The outfits: Pippa's most famous moment in Hobbs was when she wore a short-sleeved red shift dress with button detail to a Wimbledon match. The Duchess of Cambridge, meanwhile, has a plethora of Hobbs looks in her arsenal, including a standout animal-print coat dress that she wore whilst pregnant with Prince George and a classic brown belted coat that's a Winter favourite for outdoor appearances.
The label: Erdem Moralioglu's shows are a London Fashion Week hot ticket, always a cohesive mix of commercial and creative pieces with an emphasis on pretty prints, delicate fabrics, and texture. His floral prints and lace overlays appeal to Kate's girlier side, though it seems she's keeping this one for herself, as Pippa hasn't worn Erdem to a major event yet.
The outfits: While most of us can only dream of maternity looks by one of London Fashion Week's most exciting designers, Kate made this reality when she wore a simple printed sheath dress during the early stages of her pregnancy. Her most memorable Erdem look was probably the lace pencil dress she wore in Canada in 2011 that resulted in a thousand copycats. Our favourite, however, was a delicate printed dress with cap sleeves she wore in Singapore.