A series of intimate snaps, captured by photographer Sophie Margue, were shared before the big day, and the young prince had a day to remember as he tucked into a giant cake that was topped with toy trains. He even showed off his new tricycle.
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Francois looks to be the spitting image of Britain's Prince Louis in this sweet photograph. The youngster clearly enjoyed his wooden tricycle as he wheeled himself around the family's expansive garden.
It appears the little tyke is a fan of trains, with his gorgeous cake featuring a fondant train on the top. It was carrying the number two behind it. How sweet!
Francois was joined by his older brother, Prince Charles, and father, Hereditary Duke Guillaume, in their back garden, but there was another family member on full display – their chicken, which Francois looked utterly enchanted by.
In a sweet follow-up snap, the family is joined by mother, Hereditary Duchess Stephanie. Francois was the centre of attention, with Charles even placing his hand on his younger brother.
Francois took fashion inspiration from his father, with the duo both wearing navy jumpers. But while Guillaume wore tan trousers, little Francois had the sweetest pair of dungarees on.
Stephanie absolutely doted on her young son in this sweet photo.
The youngster's birthday comes shortly after his older brother marked a major milestone. Last week, the five-year-old was taken for his first royal engagement, the inauguration of a school named in his honour.
Charles was seen cutting the ribbon at the event and joining his parents for a tour of the facilities, taking great interest in a painting of a train on the wall.
The future heir to the throne was dressed smartly for his first official outing, wearing a maroon jumper and brown trousers. A particularly sweet moment saw the future heir in his father's arms as they unveiled a plaque confirming the school's name.
The youngster was also seen receiving gifts from students at the school and signing his name in the school's registry book.
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The Prince and Princess of Wales' children, Prince George, Princess Charlotte, and Prince Louis, won't be picking up this tradition at their new Forest Lodge home