Britain’s royal family is on the verge of celebrating a big birthday. On Saturday, Prince George of Cambridge, the future king of England, turns 4-years old, marking the Duke and Duchess of Cambridge Kate Middleton and Prince William’s fourth year as parents.

Despite being so young, Prince George and his sister, 2-year-old Princess Charlotte, have participated in several royal outings in the past 12 months. The siblings most recently appeared alongside their famous parents while exiting a plane after arriving at Berlin Tegel Airport on Wednesday as part of the brood’s five-day tour in Germany and Poland.

Photos from their arrival showed the young prince apparently sleepy after his journey and while Charlotte walked off the plane alone, she was later picked up by Catherine, Duchess of Cambridge. Another shot from their airport outing showed Charlotte being held by her mother as she accepted a flower. 

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Prior to their trip to Berlin, Prince George and Princess Charlotte accompanied the Duke and Duchess to Warsaw, Poland, on July 17. The family was photographed together outside Warsaw airport during their visit.

The family’s trip to Poland and Germany comes almost 10 months after Kate and William brought George and Charlotte with them to Victoria, Canada, for a eight-day royal tour. During the tour, the couple brought their offspring to a children’s party for military families on Sept. 29. There, the pair was photographed playing with balloon animals with their kids. The family of four was also spotted boarding a sea-plane on the last day of their trip on Oct. 1.

Of course, the siblings have also participated in royal family events in London as well. The family of four was photographed together enjoying the Trooping the Color parade on June 17. The royals watched the event from the balcony of Buckingham Palace alongside Queen Elizabeth II and her husband, Prince Philip. One photo from the event showed Kate putting her motherly duties on display, tidying George’s hair as he watched the show. Another photo showed Kate smiling while looking at Princess Charlotte. 

This spring also marked Catherine’s sister Pippa Middleton’s wedding to James Matthews. Kate and her two children participated in the church service at St. Mark's Church on May 20 ahead of her sibling’s reception. Photos outside the venue included Kate readying her kids before walking down the aisle. The family was also photographed outside the same church on Christmas Day last year. 

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While Duchess Catherine admits being a mom is not always easy, she said she is fully enjoying the experience of having two children. “Personally, becoming a mother has been such a rewarding and wonderful experience,” she said while speaking at Best Beginnings charity event in March, as reported by People Magazine.

“However, at times it has also been a huge challenge. Even for me who has support at home that most mothers do not,” she continued.

“Nothing can really prepare you for you the sheer overwhelming experience of what it means to become a mother. It is full of complex emotions of joy, exhaustion, love, and worry, all mixed together. Your fundamental identity changes overnight. You go from thinking of yourself as primarily an individual, to suddenly being a mother, first and foremost.”