Prince William, Kate Middleton, Prince Charles, and Camilla Parker-Bowles showed a united front when they carried a royal engagement together for the first time in nine years. Fans were delighted to see the two royal couples doing their royal duties at the Defence Medical Rehabilitation Centre (DMRC), but some noticed the Duchess of Cambridge has a habit that Prince of Wales also usually does.

As usual, Kate Middleton made everyone's jaw dropped with her Alexander McQueen ensemble. She was carrying a small blue and white handbag in her left hand, which was said to be a royal hack.

Royal etiquette expert Myka Meier revealed, via Express, that Kate Middleton has to keep her right hand free so that she can greet royal fans and hosts right away during engagements. "When entering a room or event, handbags or briefcases are held in the LEFT hand so that your right hand stays open to meet, greet and shake hands!" she explained.

Princess Diana and Camilla also do the same whenever they are performing their royal duties. However, not only the female members of the royal family follow this practice. Prince Charles even does the same. The heir to the throne has been keeping his right hand free whenever he is carrying something during a royal engagement.

Aside from that, the four royal also reportedly have coordinating signatures. When Daily Mail Rebecca English shared a snap of their signs on social media, netizens quickly pointed out the similarities between their autographs.

Prince Charles has similar writing to that of his wife, Camilla, so as Prince William and Kate Middleton. "I love how spouses' signatures match their significant others in style!" one fan commented. Another one felt stunned, seeing all of their signatures on one page. "That is so fascinating. A picture for posterity," it said.

Hello! Magazine recently reported the similarities between Prince William and Kate Middleton's signatures. Reading between the Lines author and graphologist Emma Bache noticed that although the Cambridges don't have similar personalities, they have "complementary handwritings."

According to Bache, Kate Middleton's handwriting shows a "sociable and outgoing nature," but she still enjoys her privacy. The right slant, small spaces between her written words, and tightly closed ovals reveal she has a good balance between the three zones and has a versatile personality.

Prince William's handwriting, on the other hand, is smaller but with larger spaces between the words. It only means that just like his wife, he also enjoys his privacy whenever he can. The long lower zones that pull to the right reveal she is just like Kate Middleton, who is also hardworking and has an energetic attitude. However, he is the most sensitive between them, and he will appreciate her "balanced, sensible, and nurturing nature."