Several senior members of the British royal family took to their social media accounts to greet Prince Harry on his 37th birthday, but Prince William and Kate Middleton's post stood out, and not in a good way.

Queen Elizabeth II wished her grandson well by sharing a collage of his images on Instagram stories, one of which featured his wife Meghan Markle as well. The accompanying message that included several jazzy birthday-related emojis simply read, "Wishing the Duke of Sussex a Happy Birthday today!"

Prince Charles and his wife Camilla Duchess of Cornwall also greeted his younger son through a collage of his pictures on their Instagram stories, along with a message, "Happy Birthday to the Duke of Sussex!" One of the pictures was a throwback of the Duke of Sussex as a young boy with his father, imprinting their hands at the same time into a block of concrete while on a tour of South Africa in 1997.

Meanwhile, Harry also received a birthday greeting from his elder brother Prince William and sister-in-law Kate Middleton. The Duke and the Duchess of Cambridge shared a solo image of Harry unlike other royals, and wrote "Happy Birthday Prince Harry!" adding a balloon emoji.

Royal expert Duncan Larcombe has said that William's birthday message to Harry was "curt" this year, and shows that the frosty relationship between the royal siblings has not improved.

"Short of ignoring the Duke of Sussex's 37th landmark completely, their social media post was the bare minimum from a couple who once welcomed Harry as their official Royal gooseberry. If anything, this year's birthday wishes from the Cambridges are an indication of just how far relations between the two warring clans have deteriorated over the past 12 months," he explained to the Sun.

Last year, the Cambridges had greeted Harry by sharing an image of the three of them running on a race track, alongside the message, "Wishing a very happy birthday to Prince Harry today!" In the year before that, which was before Harry had announced his exit as a senior royal, the couple had shared a picture of William and Harry sharing a laugh at the latter's wedding to Meghan Markle.

Larcombe says he was surprised with William and Kate's choice of the picture in this year's message as he expected them to use one of Harry and William from the last time the brothers were together for the unveiling of their mother Princess Diana's statue in July this year.

"That would have sent a message of unity and the shared common bond between siblings who were once as thick as thieves," he said.

British royal family at Commonwealth Day service
British royal family at Commonwealth Day service Photo: POOL / Phil Harris