Little Prince Louis was all smiles on his first day of school. The youngest of Prince William and Kate Middleton’s three children has followed in his older siblings’ footsteps and recently began attending Willcocks Nursery School in London. “Kate and William were a little nervous about how he’d adapt, but they had nothing to worry about,” says a royals insider.

Louis, who turned 3 on April 23, feels like a big boy now. “He’s opinionated and bright for his age, but loves to make those around him laugh!” says the insider. “William jokes that he’s the comedian of the family.”

A REASON TO CELEBRATE

Following their sorrow over the recent death of Prince Philip, Kate, 39, and William, 38, threw themselves into creating a special birthday party for Louis with their older kids, Prince George, 7, and Princess Charlotte, 5. “Kate made mini sausages, burgers, pizza slices, mac ’n’ cheese and chicken bites for the family to enjoy outside,” says the insider. “She also baked a huge multicolor birthday cake.”

The birthday boy received a gardening set from brother George and a water toy — much like a Slip ’N Slide — from his sister Charlotte. But the real working digital camera his parents gave him quickly became Louis’ favorite gift. “He shares Kate’s passion for photography,” confides the insider. “Now he takes the camera with him everywhere.”

Louis has become an outgoing and cheerful little charmer. “He’s absolutely loving school and is having no problem fitting in,” says the insider. “Personality wise, he takes after Charlotte more than George — they both share the same naughty streak and ooze confidence. And now that he’s 3, Louis feels so grown up!”

— Reporting by Natalie Posner