Kate Middleton In Issa(01 of34)
Open Image ModalPrince William And Kate Middleton, During A Photocall In The State Apartments Of St James's Palace, London To Mark Their Engagement. (credit:Mark Cuthbert via Getty Images)
Pippa Middleton In Issa(02 of34)
Open Image Modal (credit:PA )
The Duchess Of Cambridge In Alexander McQueen Ivory Coat(03 of34)
Open Image ModalCatherine, Duchess of Cambridge carries her son Prince George Of Cambridge alongside Prince William, Duke of Cambridge, following his christening at the Chapel Royal in St James's Palace on October 23, 2013. (credit:WPA Pool via Getty Images)
Pippa Middleton In Suzannah Crabb Ivory Coat(04 of34)
Open Image ModalPippa and James Middleton the bother and sister of Britain's Kate Duchess of Cambridge arrive at the Chapel Royal in St James's Palace, London for the christening their nephew Prince George. (credit:ASSOCIATED PRESS)
Kate Middleton In Alexander McQueen(05 of34)
Open Image ModalMiss Catherine Middleton arrives at Westminster Abbey for the Royal Wedding in London on Friday April 29, 2011. (credit:ASSOCIATED PRESS)
Pippa Middleton In Alexander McQueen(06 of34)
Open Image ModalPrince Harry and Pippa Middleton leave Westminster Abbey after the wedding ceremony of Prince William and his new bride Kate on Friday April 29, 2011. (credit:ASSOCIATED PRESS)
The Duchess In Emilia Wickstead(07 of34)
Open Image ModalPippa Middleton In Emilia Wickstead(08 of34)
Open Image ModalPippa Middleton attends the Sugarplum Ball at One Mayfair on November 20, 2013 in London, England. (credit:Gareth Cattermole via Getty Images)
The Duchess In Temperley London(09 of34)
Open Image ModalBritain's Kate the Duchess of Cambridge arrives for an Autumn gala evening dinner and reception in aid of Action on Addiction at L'Anima Restaurant in London, England, Thursday, Oct. 23, 2014 (credit:ASSOCIATED PRESS)
Pippa Middleton In Temperley London(10 of34)
Open Image ModalPippa Middleton sighted at Temperley London Show during London Fashion Week S/S 2012 on September 19, 2011. (credit:Neil Mockford via Getty Images)
The Duchess In Beulah London(11 of34)
Open Image ModalCatherine, Duchess of Cambridge attends a Service of Commemoration to mark the end of combat operations in Afghanistan at St Paul's Cathedral on March 13, 2015. (credit:Max Mumby/Indigo via Getty Images)
Pippa Middleton In Beulah London(12 of34)
Open Image Modal Pippa Middleton attends her book launch party for 'Celebrate' at De Vries Boekhandel on December 11, 2012. (credit:Helene Wiesenhaan via Getty Images)
The Duchess In Zara(13 of34)
Open Image ModalBritain's Kate, the Duchess of Cambridge, waves as she and Prince William arrive at Viaduct Basin in Auckland, New Zealand, Friday, April 11, 2014. (credit:ASSOCIATED PRESS)
Pippa Middleton In Zara(14 of34)
Open Image ModalPhilippa Middleton departs the Goring Hotel in London on April 30, 2011 in London, England. (credit:Ian Gavan via Getty Images)
The Duchess In Project D London(15 of34)
Open Image ModalCatherine, the Duchess of Cambridge, smiles during a ceremony to mark her and her husband's, Britain's Prince William, farewell from Tuvalu in the Vaiaku Maneapa before departing from Funafuti on September 19, 2012 (credit:AFP via Getty Images)
Pippa Middleton In Project D London(16 of34)
Open Image ModalPippa Middleton sits in the Royal Box during the Gentlemen's Singles final match between Roger Federer of Switzerland and Andy Murray of Great Britain on day thirteen of the Wimbledon Lawn Tennis Championships at the All England Lawn Tennis and Croquet Club on July 8, 2012 (credit:Clive Brunskill via Getty Images)
The Duchess In A Beulah London Red Plunge Dress(17 of34)
Open Image ModalPrince William, Duke of Cambridge (L) and Catherine, Duchess of Cambridge (R) attend a fundraising Gala (credit:Handout via Getty Images)
Pippa Middleton In A Temperley London Red Plunge Dress(18 of34)
Open Image ModalPippa Middleton Arriving At The Boodles Boxing Ball At Park Plaza Westminster Bridge Hotel, London. (credit:Mark Cuthbert via Getty Images)
The Duchess In Roksanda Illincic(19 of34)
Open Image ModalCatherine, Duchess of Cambridge attends the UK's Creative Industries Reception at the Royal Academy of Arts on July 30, 2012 (credit:WPA Pool via Getty Images)
Pippa Middleton In Roksanda Illincic(20 of34)
Open Image ModalPippa Middleton launches her new creative entertaining book 'Celebrate' at an afternoon children's party held at Daunt Books, Fulham Road on October 25, 2012 (credit:David Levenson via Getty Images)
The Duchess In L.K.Bennett(21 of34)
Open Image ModalCatherine, Duchess of Cambridge visits the Royal Australian Airforce Base at Amberley on April 19, 2014 in Brisbane, Australia. (credit:Samir Hussein via Getty Images)
Pippa Middleton In L.K.Bennett(22 of34)
Open Image ModalPippa Middleton on the cover of Hello! Magazine (credit: Hello! Magazine)
The Duchess In Hobbs(23 of34)
Open Image ModalBritain's Catherine, Duchess of Cambridge, arrives for a visit of the Resort Studios in Margate, southern England on March 11, 2015. (credit:ARTHUR EDWARDS via Getty Images)
Pippa Middleton In Hobbs(24 of34)
Open Image ModalPippa Middleton attends the quarterfinal round match between Roger Federer of Switzerland and Jo-Wilfried Tsonga of France on Day Nine of the Wimbledon Lawn Tennis Championships. (credit:Julian Finney via Getty Images)
The Duchess In Ted Baker(25 of34)
Open Image ModalKate Middleton attends day 4 of the Cheltenham Horse Racing Festival on March 14, 2008 in Cheltenham, England. (credit:Max Mumby/Indigo via Getty Images)
Pippa Middleton In Ted Baker(26 of34)
Open Image Modal (credit:Twitter/Perth Fashion)
The Duchesss In Susannah(27 of34)
Open Image ModalCatherine, Duchess of Cambridge holds Prince George as he and Prince William, Duke of Cambridge's look on while visiting the Sensational Butterflies exhibition at the Natural History Museum. (credit:WPA Pool via Getty Images)
Pippa Middleton In Susannah(28 of34)
Open Image ModalThe Duchess In Whistles (Dress)(29 of34)
Open Image ModalCatherine, Duchess of Cambridge is seen after viewing artist Paul Emsley's new portrait of herself during a private viewing at the National Portrait Gallery (credit:WPA Pool via Getty Images)
Pippa Middleton In Whistles (Coat)(30 of34)
Open Image Modal Pippa Middleton is seen on September 28, 2011 in London, England. (credit:SAV via Getty Images)
The Duchess In A Collette Dinnigan Red Lace Dress(31 of34)
Open Image Modal (credit:Sunday Express/What Kate Wore)
Pippa Middleton In A Carolina Herrera Red Lace Dress(32 of34)
Open Image ModalPippa Middleton attends the British Heart Foundation's Roll Out The Red Ball at Park Lane Hotel on February 10, 2015. (credit:Tim P. Whitby via Getty Images)
The Duchess In Katherine Hooker(33 of34)
Open Image ModalCatherine, Duchess of Cambridge attends the East Anglia's Children's Hospices (EACH) Norfolk Capital Appeal launch event (credit:Max Mumby/Indigo via Getty Images)
Pippa Middleton In Katherine Hooker(34 of34)
Open Image ModalPippa Middleton attends Day 3 of The Cheltenham Festival at Cheltenham Racecourse (credit:Max Mumby/Indigo via Getty Images)