Plus, how the Duke of Sussex plans to ring in his milestone birthday.

As Prince Harry approaches his milestone 40th birthday on Sept. 15, he’s setting his sights on the future.

After years of self-reflection – chronicled in his best-selling memoir Spare – the Duke of Sussex is focused on enjoying life with wife Meghan Markle and their children, Prince Archie, 5, and Princess Lilibet, 3.

His work continues with his Archewell Foundation, the non-profit he co-founded with Meghan, and a series of entertainment projects through their Netflix deal, including an upcoming documentary airing in December that’s centered on one of his greatest passions – polo.

But above all, Prince Harry’s priority remains fatherhood. In reflecting on his birthday, Harry tells PEOPLE via his spokesperson: “The best gift I’ve ever been given is, without doubt, my kids. I enjoy watching them grow every single day and love being their dad.”

Harry plans to celebrate his big day with Meghan and their children, followed by a gathering with close friends internationally.

Though the Duke and Duchess of Sussex are raising Archie and Lilibet out of the spotlight, they have given glimpses into their children’s personalities. During their trip to Colombia in August, Meghan connected with a kindergartener when she said the student was the “same age” as her son and voiced her pride on the Afro-Descendent Women and Power panel that Lili “found her voice.”

As Harry fights for increased security for their family of four, the echoes of the 1997 death of his mother, Princess Diana, in a high-speed car chase weighs heavily, particularly now that he is a parent.

“Harry has been reluctant to show his children publicly, not out of a desire to hide them but to protect their privacy and safety from potential threats,” a friend previously told PEOPLE. “He wants them to lead as normal a life as possible without the fear of kidnapping or harm.”

The friend added, “As a dad and husband, Harry is determined to ensure that history doesn’t repeat itself.”

Despite recent speculation, a return to royal duties is not on the horizon for Harry as he steps into his forties. With ongoing tensions between him, his father King Charles, and brother Prince William, Harry is happy with his life in Montecito, California, where he’s raising his young family with Meghan, 43, and continuing their shared work.

His schedule also includes an upcoming visit to New York City later this month on behalf of several projects close to his heart, including the organization behind Princess Diana’s legacy award.