These royal relatives were absent from the Commonwealth Day Service

The annual Commonwealth Day service took place at London's Westminster Abbey on 13 March, which will be the location for King Charles III's Coronation in May. 

The monarch attended the event with his wife Queen Consort Camilla, as well as Prince William and Kate Middleton, who are now known as the Prince and Princess of Wales since the late Queen Elizabeth II passed away in September last year. 

Prince Edward and Sophie Wessex - who have since acquired the Duke and Duchess of Edinburgh titles - as well as Princess Royal, Anne, and her husband  Timothy Laurence.

However, some royals were absent from the event, according to The Mirror Online. 

Eagle-eyed royal fans may have noticed William and Kate's three children, Prince George, Prince Louis, and Princess Charlotte were not present at the ceremony. 

But, there is a valid reason. 

The royals have yet to officially confirm why their brood were absent, however, it is believed the trio would have had to miss school to attend, and the timing of the service would have clashed with their lessons. 

George, Charlotte and Louis now attend Lambrook School in Berkshire, which was part of the reason the family moved to Windsor to attend the same school together. 

They were not the only royals absent from the Commonwealth Day event, as Prince Harry, Meghan Markle, and their children Prince Archie and Princess Lilibet missed the service, as they live stateside. 

Charles, 74, is now the head of the Commonwealth, and the theme for Commonwealth Day this year is "forging a sustainable and peaceful common future”. 

Speaking at the service, which has been obtained by The Times, the British monarch, said: "Commonwealth Day was an occasion of particular pride for my beloved mother, the late Queen; a treasured opportunity to celebrate our Commonwealth family, to whose service she dedicated her long and remarkable life.

“The Commonwealth has been a constant in my own life, and yet its diversity continues to amaze and inspire me. Its near-boundless potential as a force for good in the world demands our highest ambition; its sheer scale challenges us to unite and be bold.”

This week is the 10th anniversary of the Commonwealth Charter, which prides itself on "peace and justice; tolerance, respect and solidarity; care for our environment, and for the most vulnerable among us."

Charles added: "These are not simply ideals. In each lies an imperative to act, and to make a practical difference in the lives of the 2.6 billion people who call the Commonwealth home."