Harry and Philip are known to have a very strong relationship, and last week the Sussex's Instagram account wished "Grandpa" a happy birthday.
Scroll down to see how some of your favourite celebrities marked yesterday.
William, 37, took to Instagram to share the pic of his youngest son Louis playing on a swing, and another of his father, Prince Charles, 71, stepping off a helicopter, alongside the caption: "Happy father's day".
These royals' sartorial choices are never an afterthought so, believe us, there's definitely a deeper meaning than just a wedding ring here.
The chapel is close to the couple's home - Frogmore Cottage - in Home Park. In an extra sweet touch, Archie can be seen reaching out to grab ahold of one of his father's fingers.
It's not the first time that Her Majesty has had to miss a family christening. It's been worn by 62 royal babies, including Harry and brother William, but after all those years and diapers, a replica needed to be created.
The Dean of Windsor, the Rev David Conner, and Justin Welby, the Archbishop of Canterbury, are reportedly conducting the ceremony.
Meghan Markle added: "It's magic, it's pretty fantastic". Impressing the Duke of Edinburgh was very important for Meghan, so she took time to learn more about him and his family.
However, Meghan's mum Doria Ragland will be flying in from California to make the big day.