Today is not just any day for Kate Middleton—it's her 40th birthday!

In honor of the milestone, various members of the royal family have sent their well wishes to the duchess, one of which included none other than Queen Elizabeth II. Her Royal Majesty shared a series of photos to the royal family Instagram account, and there seems to be a special meaning to this birthday post.

Instead of posting a generic assortment of pics featuring the Duchess of Cambridge, the four snaps capture the close relationship between Middleton and the queen. All of the photos either display the two smiling and laughing, or engaging in an intimate conversation. This seems to be an indication of the positive feelings they share for one another and specifically the warm feelings the queen has for Middleton.

The caption of the post reads, “Wishing The Duchess of Cambridge a very happy 40th birthday today!”

The photos depict close moments between the two royals throughout the years, one of which occurred just this past June, when they attended a G7 Leaders Summit reception with Camilla Parker Bowles and Queen Elizabeth decided she was going to try to cut the sheet cake with a sword.

It's become evident that these two have a tight-knit relationship, given that the queen often lends Middleton her earrings and they share similar passions, like photography. According to a report from Us Weekly back in October, a source revealed that Queen Elizabeth “feels confident that Kate will make a great queen” and she and the duchess have “developed a great relationship.”

We hope these two get the chance to celebrate Kate's birthday together.

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RELATED: QUEEN ELIZABETH'S CHEFS JUST SHARED HER FAVE CHOCOLATE BIRTHDAY CAKE RECIPE

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