A new report in one of Britain's most popular gossip magazines claims Kate Middleton is pregnant with twin girls, less than a year after the birth of Prince George.

According to the latest issue of OK! Magazine, Kate and her husband Prince William, who welcomed their first child in July, are calling the second pregnancy a "dream come true."

"Kate has always wanted a daughter, and she's talked about it so much that William did too," a palace insider said.

"Kate's upbringing with Pippa [Middleton] was idyllic and she always wanted to have girls of her own to carry on the legacy of strong, happy women. Plus, she thinks George having sisters will be tremendously good for his character."

Last month, Prince George attended his first royal engagement in Wellington, New Zealand and he was seen playing and sharing toys with other babies.

Prince George on his first official royal engagement in Wellington, New Zealand. James Whatling-Pool/Getty

"Kate was so worried that George would not want to play with strangers," a source said. "But the way he was so sweet and loving really calmed her down.

"Seeing him so confident with other children, readily sharing toys, made her realise what a wonderful big brother he's going to be. She couldn't be happier about it."

Adding on, the report claims that the 87-year-old monarch is also excited about the news.

"Queen Elizabeth has been keeping jewelry and gifts for years now, just in case William ever had a daughter," the insider revealed.

"It's a tradition in the family. The new princesses will inherit priceless antique diamonds and artwork. There's also a stunning cradle that once belonged to Queen Victoria and a silver rattle handed down from the late queen mother."

Kate was last rumoured to be expecting twins in March, when OK! reported that she was "14 weeks along".