Prince William didn't need any reminders for today's special significance.
The duchess is expected to celebrate her birthday quietly this evening at home with William and their three children. In fact, she took a leave from her duties after announcing that she was pregnant with Prince Louis.
Charlotte goes to Willcocks Nursery School, while George goes to Thomas's London Day School in Battersea.
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During that timeframe, players can download the demo and experience a playable slice of the full game starring Leon Kennedy. Once it's over, you'll (theoretically) have to wait until the Resident Evil 2 remake comes out on January 25 to play more.
When someone asked what the royal would be doing to mark Kate's big day, he jokingly replied, "That would be telling!"
A year ago the heavily pregnant Duchess spent the day with her family at Kensington Palace.
George will be celebrating his sixth birthday in July, while baby Louis, turns one on April 23.
It's also likely the extended Cambridge family will join in on the celebrations.
The Cambridges' youngest child Prince Louis is now only eight months old, which makes it even more unlikely that Kate is pregnant again.
It's not known what William gave Kate for the birth of their third child Prince Louis, but there was some speculation she received a citrine ring - as she was pictured wearing it at the wedding of Meghan and Harry in May 2018. Kensington Palace announced that the organization named the 36-year-old duke a patron of London's Air Ambulance 30th Anniversary Campaign.