LONDON - British royals Prince William and Kate Middleton have shared a relaxed photograph of their family for their annual Christmas card.

Dressed in sweaters, Prince William, 38, second-in-line to the throne, is pictured with his wife Kate, 38, and their three children - George, 7, Charlotte, 5, and Louis, 2 - sitting with wide grins on a bale of hay in front of chopped firewood at their Amner Hall country home in England.

Youngest son Louis however sits front and centre and steals the limelight with a cheeky, mid-laugh grin.

According to People.com, the couple sent one of their cards to Britain's National Health Service, which included a handwritten message from Prince William thanking them for their work during the coronavirus pandemic.

"To all the amazing NHS staff. We can never thank you enough for the dedication and sacrifices you have had to make this year. We will be forever grateful," he wrote.

The whole Cambridge family also made a surprise appearance at a pantomime performance at London's Palladium Theatre earlier this month to thank essential workers, marking the children's first public appearance in months.

"It is the least we could do to thank you for everything you do - day in, day out - to keep our country safe and look after those who need help the most," Prince William said in a speech before the event.