"Last year it was her birthday in lockdown, but this year we were able to have one other family over," William said

Prince William is opening up about daughter Princess Charlotte's 6th birthday celebrations!

On Tuesday, William visited Babcock Vehicle Engineering to learn about the company's important role during the COVID-19 pandemic, when they created a new prototype of ventilators. The company's lead HR business partner Jenna Jackson asked the royal dad about Princess Charlotte's birthday on Sunday.

"She had a lovely day, thank you," said William, 38, according to Hello! "Last year it was her birthday in lockdown, but this year we were able to have one other family over. They grow up very fast. It was great fun."

In a new portrait taken by mom Kate Middleton and released in honor of her birthday, Princess Charlotte bears a striking resemblance to her father.

Princess Charlotte
Princess Charlotte
| Credit: Duchess of Cambridge/PA
Prince William, Princess Charlotte
Prince William; Princess Charlotte
| Credit: Tim Graham Photo Library via Getty; Duchess of Cambridge via Getty

Photos of Prince William around the same age show off their similarities, from that gleam in their eyes to their cheeky grins.

Even William and Kate are aware of Charlotte's mini-me status. During the couple's Jan. 2020 visit to Bradford, they stopped by the Khidmat Centre — where a special dessert display was revealed. The couple was astonished by an elaborate red, white and blue cake surrounded by cupcakes, each of which featured photos of Kate and William.

The cake creator explained to the pair that each snapshot was a different moment from their lives, from their childhoods to becoming parents themselves.

"Is that me?" Prince William said while pointing to a portrait of himself as a youngster, before commenting that it looked like his daughter. "Because that looks just like Charlotte. That is incredible."

Kate was in agreement: "It looks so much like Charlotte."

Princess Charlotte; Prince William, Duke of Cambridge
Princess Charlotte and Prince William
| Credit: Aaron Chown - WPA Pool/Getty Images

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The family likely spent the weekend at their country home, Anmer Hall, on Queen Elizabeth's Sandringham estate in Norfolk – around 100 miles north of London – as it was a long weekend with a public holiday on Monday in the U.K.