Prince William and Kate Middleton's firstborn celebrated his seventh birthday on Wednesday. His latest pictures as released by Kensington Palace show him to be all grown-up.

A source told Us Weekly that Princess Charlotte and Prince Louis' older brother has grown up to become "mature" and "a protector of siblings."

The Cambridge family has not stepped out together in public for a long time. The family-of-five continues to isolate themselves in their countryside home due to coronavirus pandemic. A source revealed that Prince George has grown up to become a mature and confident boy and Charlotte is the "most self-assured at" out of the three siblings.

"George has come out of his shell and is a confident little boy – although Charlotte is the most self-assured at of the three," the insider said.

The source goes on to describe George as kindly and protective brother to his siblings. "He's kind natured and thoughtful and looks out for his brother and sister," the insider added.

Nevertheless, the heir to the throne has developed a "competitive streak" during his time with family in the lockdown. He apparently wants to be "best at everything."

"Kate and William joke that he 'likes to be the best at everything,'" the source said. He is said to be showing signs of being a "high achiever." It is believed that this trait will "come in handy" for George later in life when he takes the throne after his grandfather Prince Charles and father Prince William.

Prince George reportedly had an unusual birthday celebration this year. The younger royal reportedly enjoyed an intimate themed party that was organised by his parents.

For their son's special day, the Duke and the Duchess of Cambridge "organized a small camping-themed BBQ party" in tents in the garden of the Cambridge's Norfolk home. The family-of-five was joined by the duchess' parents Michael and Carole Middleton and George received some exciting gifts from his loved ones.

Prince George
The Duke and Duchess of Cambridge have released an official portrait of Prince George to mark his 4th birthday AFP/Getty

As per the report, the little prince received a yurt from his parents and a new bicycle from his siblings. They even baked a cake together for the birthday boy that was topped off with "sprinkles, lollipops, and colourful candy."