For proof, look no further than Prince George's official birthday photo.
The picture, tweeted by Kensington Palace, was accompanied by a message of thanks from the duke and duchess to everyone for their "lovely messages".
A few months after his last birthday George started his first day at school with his father, but without his mother, Kate.
Prince George was christened on 24 October in a private family ceremony.
The nine-month-old prince embarked on his first royal tour with his parents in April 2014 to New Zealand and Australia.
Despite being in force since 2013, the birth of Louis this year brought the act into place for the first time since its creation.
Where is Prince George in the line of succession?
When former US President Barack Obama and his wife Michelle visited England in 2016, they couldn't resist meeting George.
The youngster has just completed his first year at school, attending Thomas's Battersea in south London.
Bundled up in a white blanket, the little Prince was cradled by his proud parents as he was introduced to the media and adoring crowds who had awaited his arrival.
Prince William was an RAF search and rescue pilot.