Prince George resembles Prince William in new birthday portrait taken by Kate Middleton

The British royal family is celebrating the 11th birthday of Prince George, second in line to the throne after his father, Prince William.

Prince George is 11!

Per tradition, a portrait of the future heir to the throne was released on the Prince and Princess of Wales' social media on Monday. This year's selection was a black-and-white picture of the young prince in a suit, taken by the boy's mother, Kate Middleton, a major departure from his more relaxed look at 10.

Viewers marveled at how the young prince resembled many of his relatives – Prince William, James Middleton (the Princess of Wales' brother), and Charles Spencer (the brother of the late Princess Diana). 

PRINCE GEORGE'S 11TH BIRTHDAY MARKS LAST YEAR BEFORE 'MORBID RULE' KICKS IN: EXPERT

Christopher Andersen, author of "The King," previously told Fox News Digital that a soccer game would likely be incorporated into George's birthday celebrations, given the prince's affinity for the sport. 

"William and Kate have done pretty much anything they could to make George's childhood a relatively normal one – as they have with all their children," Andersen explained. "But this has obviously been a tough year for George, Charlotte and Louis, with both their mother and their grandfather waging very public cancer battles."

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"So, it's likely they'll stick to the usual plan and have a low-key party at Windsor attended by cousins and a few school friends," he shared.

Andersen also noted that this was a transitional year for Prince George – the final before a "morbid rule" is implemented for the boy's safety.

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"This may be the last year George will be allowed to fly with his father," Andersen said. "Starting at age 12, heirs to the throne are required to take air trips separately to preserve the line of succession should an accident occur."

"When William turned 12, he began flying in a separate royal jet apart from his father and brother Harry," Andersen explained. "It's a morbid rule, but then again, when they turn 16, all senior royals are also asked to help plan their own funerals."

Prince George is second in the line of succession, following his father, Prince William.