Duke and Duchess of Sussex Share Adorable New Photo of Baby Archie For Prince Charles' Birthday

Prince Charles, who is next in line to the British throne, turned 71 on Thursday.

Happy birthday, grandpa! 

That's the sweet message behind a new photo of baby Archie shared in honor of Prince Charles' 71st birthday.

"Happy birthday to His Royal Highness The Prince of Wales - Sir, Pa, Grandpa!" the Duke and Duchess of Sussex captioned the photo on Instagram. 

The photo is from baby Archie's July 6 christening and shows proud dad Prince Harry and grandpa Prince Charles beaming down at the little one. 

Prince Harry and Duchess Meghan Markle have generally kept Archie out of the public eye, but he did accompany his parents to meet human rights activist Archbishop Desmond Tutu in South Africa this summer. 

The duchess has been candid about the challenges she's faced as a new mother in the spotlight, and many women have rushed to support her.

Last month, more than 70 female members of Parliament wrote a letter to Markle expressing their solidarity with her as she battles hurtful coverage in the press. 

More recently, Markle visited Luminary Bakery, an East London organization that helps train and employ women who have experienced poverty. 

"I find that when you strip all the layers away, as people, and especially as women, we can find deep connection with each other, and a shared understanding," Markle told those gathered at the event.