"He looks like a big boy in blue and she looks so pretty – they look so gorgeous together," British children's wear designer Rachel Riley tells PEOPLE exclusively

By Monique Jessen
Updated June 06, 2015 05:10 PM
Advertisement
Courtesy Duchess of Cambridge

The George Effect rolls on – with Princess Charlotte joining her brother as a budding trend-setter.

With the release of Charlotte’s first official portrait on Saturday, the royal siblings reprised several of their go-to looks.

(Yes, even at 22 months and 5 weeks, George and Charlotte have go-to looks.)

Seeing the two perfectly coordinated royal siblings together for the first time, “he looks like a big boy in blue and she looks so pretty,” British children’s wear designer Rachel Riley, whose clothes George wears in the portraits, tells PEOPLE exclusively.

“They look so gorgeous together,” she adds.

(As if we expected anything less!)

For big brother George, royal mom Princess Kate opted for the same shorts and shirt set from her son’s adorable hospital look after Charlotte’s birth on May 2. The British designer has been a favorite of Kate’s since she dressed George in a Rachel Riley sailboat dungarees on his first royal play date last year.

“We are absolutely thrilled,” Riley says of seeing George in her $159 short-and-shirt set with blue piping and neat buttons.

Made of soft cotton pique, “the shorts are baby cord with turn-ups at the bottom,” says Riley. “The shorts are buttoned onto the shirt.”

Related Video: Royal Flashback: Prince William and Prince George’s Christenings

And fans of “Christopher Robin” socks can rejoice: George again wears the $11 pair from Amaia that made such a splash outside the hospital and in an earlier portrait.

The socks – which have been ordered from as far away as Australia – “are very popular,” Segolene Tresca, co-owner of Amaia, the boutique in London’s Chelsea Green where Kate does much of her shopping, tells PEOPLE exclusively. “We have been selling a lot of socks still!”

The future king’s shoes are Start Rite’s "Jo"-style first walking shoes, which sell for $56.

As for Charlotte, she’s wearing a jersey top with frill detail in Swiss batiste – a soft, semi-sheer cotton – and wool sweater from Spanish children’s wear and home goods boutique Irulea.

The sweater and shirt is part of a $254 four-piece ensemble – including the bonnet that Charlotte famously wore backward to make her public debut – and is now called the “Princess Charlotte” set on Irulea’s web site.

With reporting by NINA BIDDLE

Want to keep up with the latest royals coverage? Click here to subscribe to the Royals Newsletter.