updated 07/19/2014 AT 1:00 PM ET
•originally published 07/21/2014 AT 2:30 PM ET
As Prince George turns 1, he’s walking, babbling and boldly exploring the world. But Princess Diana’s former astrologer, Penny Thornton, says the stars hold big changes for the little prince in the year ahead – including a baby brother or sister.
“The first big thing that is going to happen to him is the arrival of a new baby brother or sister which will almost certainly be next year,” Thornton tells PEOPLE.
“The advent of a new sibling will make a big difference to George because he will be knocked off his pedestal, but already we can see he is a charming, outgoing, confident little person.”
The rumor mill is already on overdrive about Prince William and Kate’s plans to expand their family. Recently, British bookmakers stopped taking wagers on a pregnancy announcement, fueling speculation. The Palace has not commented on the couple’s family plans, but a friend has confirmed to PEOPLE that they want another baby in the not-too-distant future.
Thornton has been surprised by George’s outgoing personality, most recently displayed during the royal family’s April tour Down Under. “As a Sun Cancer with Moon in Capricorn and Scorpio rising, I expected him to be strong and fixed in purpose,” she says. “But I didn’t expect to see him so comfortable in the public eye. I think it shows how well Kate and William have brought him up.”