Kate Middleton
Kate Middleton dressed her kids Prince George and Princess Charlotte with old-fashioned clothes to make them look timeless. Pictured: Prince William, Prince George, Middleton and Princess Charlotte on the tarmac of the Airbus compound in Hamburg, northern Germany, on July 21,2017. Getty Images/Patrik Stollarz

Kate Middleton has a reason why she prefers to dress her children in old-fashioned clothes.

According to Josie Griffiths, a journalist for the Sun, the Duke and Duchess of Cambridge's eldest son is usually dressed in collared shirts, braces and shorts with his signature long socks. On the other hand, their 3-year-old daughter usually wears frocks. And there is a reason why their mother dresses them this way.

Middleton has used Rachel Riley's design for Prince George. According to the designer, Prince William and Middleton go for "classic and timeless" when it comes to their children's wardrobe. "The reason why I design clothes that way is because if they wear very simple things, it's about the child, and it's timeless in that you can't really date a specific photo or put them in something that seems out of date," she told the Telegraph. "I think [Kate and Prince William] are going for clothing that is classic and timeless, rather than clothes that draw attention to them."

Middleton is also popular for dressing her children in hand-me-downs. For instance, in May, she released a photo of Princess Charlotte kissing her new sibling, Prince Louis. The photo was reminiscent of Prince George kissing his baby sister back in 2015. In the snap, Princess Charlotte wore Prince George's navy cardigan, which he wore in a Vanity Fair photo with Queen Elizabeth II for the monarch's 90th birthday. On the other hand, Prince Louis wore the jumper Princess Charlotte sported in her first photo with big brother, Prince George.

In related news, Middleton and Princess Charlotte love to wear coordinated outfits. The Duchess of Cambridge and her only daughter have been seen on multiple occasions wearing similar wardrobe.

"When you're the most photographed family on the planet (sorry Beyoncé, Jay-Z and Blue Ivy) coordinating your look is a great way to preserve the Cambridge family's brand," said Damien Woolnough, 9Style's editor.

"Just like the Beckhams, Kate and Will demonstrate that the family that dresses together looks great together," the expert added. "To stop the whole thing from looking too matchy-matchy, the colour choices are just close enough to make a strong impression without being spot on."