Prince Charles got in on the celebratory posts for his grandson's birthday! Prince Louis turned 2-years-old on Thursday, and we already saw a great series of photos posted by his parents on the Kensington Royal Instagram account.

But the Prince of Wales had a heartwarming photo of his own to contribute to Louis' big day. Check it out below.

Prince Charles & Prince Louis birthday picture

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The photo was captioned: "The young Prince enjoys a hug from his Grandfather, The Prince of Wales."

It also notes that photo credits go to the Duchess of Cambridge, meaning that Kate Middleton snapped the picture of her son with his grandfather.

According to Hello!, attentive followers of the royal family noticed this photo during Prince Charles's live stream opening of the Nightingale Hospital last week. But many suspected it was Prince George hugging his grandfather, so the birthday post for Louis came as a surprise.

In case you missed them, Prince William and Duchess Kate shared some very cute photos of their son on his birthday too.

Prince William and Duchess Kate share new Prince Louis photos

RELATED: George, Charlotte & Louis Send the Queen "Chatty" Videos

Royal family birthdays: Busy in April and May

In the past few years, the end of April and beginning of May have become a busy few weeks for royal birthdays! Queen Elizabeth II celebrated her 94th birthday on April 21, Louis on the 23rd, and then baby Archie will turn 1 on May 6.

You can also check out the very best photos of Prince Louis right here!