Once the photos were released, many royal fans questioned why Her Majesty was absent from the portraits.
Well, according to former royal correspondent Duncan Larcombe, it's all to do with etiquette.
"The main reason is that it's Prince Charles' birthday portrait, so he should be the most senior member of the royal family to appear in it," Duncan told Harper's Bazaar.
"There's also more evidence than ever that there's a conscious effort to start pushing Charles to the front as he takes on a more prominent role."
Taken in the gardens of Clarence House, Charles and Camilla sit at the front with Prince George and Princess Charlotte beaming.
Prince William and Kate are positioned behind, with Kate cradling now seven-month-old Prince Louis.
Prince Harry and pregnant wife Meghan stand behind Camilla - and in one of the shots Meghan is leaning over laughing.
Prince Charles, over the past year, has been gradually taking on some of his mother's responsibilities. This included laying the Queen's wreath at the Cenotaph memorial, both in 2017 and last week on Remembrance Sunday.
And while eagle-eyed fans might have noticed Her Majesty and Prince Philip were also absent from Prince Louis' official christening photos in July, this was said to be agreed between the Queen, Prince William and Kate at the time and was not due to health reasons.