If you don't know, Duchess Kate is going to be celebrating her birthday in just a few days on January 9!
Kate previously wore the coat while pregnant with her youngest child, Prince Louis, in February of previous year.
In the 2018 Amazon Prime documentary "William & Kate: the Journey", royal biographer Katie Nicholl revealed how the Duchess of Cambridge's stunning looks sparked rumors when she and Prince William first stepped out to show their newborn daughter to the world.
Charlotte goes to Willcocks Nursery School, while George goes to Thomas's London Day School in Battersea.
IAN VOGLER via Getty Images The Duke of Cambridge walks across the helipad after arriving in a red London Air Ambulance at the Royal London Hospital in east London on January 9.
William will reportedly join his wife and family during the evening to mark Middleton's big day.
The palace wished Middleton a happy birthday on the palace and the royal family's official Twitter accounts.
The charity, which delivers a trauma team to critically injured people in London, is close to William's heart.
Prince William, a former pilot with the air ambulance service in East Anglia, flew from Kensington Palace for 25 minutes before landing on a helipad at the Royal London Hospital.
After his engagement, he will no doubt be heading off to celebrate with his wife and kids.
The Royal Family's page chose a series of five smiley photos of Kate.
Kensington Palace thanked the public for their "lovely messages".