Kate Middleton
Catherine, the Duchess of Cambridge.Reuters

Rumours of the gender of the second royal baby has started doing the rounds once again, and according to a new report Prince William and wife Kate Middleton are expecting twin girls this time around.

Clarence House announced in early September that Middleton was pregnant with the second royal baby, and as with her first pregnancy, the Duchess was suffering from Hyperemesis Gravidarum, an extreme case of morning sickness.

And now, Star magazine's 20 October issue claims that the royal couple found out that they were expecting twins in a recent ultrasound.

"When they looked at the screen and saw two tiny human beings, they were completely overwhelmed," a long-time friend of the couple told the magazine, according to HollywoodLife.

"Will said Kate's mouth dropped open and her eyes almost popped out of her head, then she squealed, 'Oh my God!' He'll never forget the look on her face — it must have been priceless!"

The magazine added that the Duke and Duchess of Cambridge have shared this wonderful news with their family and close friends. "William phoned his father straightaway to give him the good news," the insider revealed, adding that Queen Elizabeth was informed in person.

Interestingly, this is not the first time news of the royal couple expecting twins have hit the media. Back in May, OK! Magazine reported that the Duchess has always wanted a girl child, and Prince William shared her desire.

"Kate has always wanted a daughter, and she's talked about it so much that William did too," an insider told the magazine. "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."

At the time, it was reported that Queen Elizabeth has already started putting away gifts to give the newest addition to the royal family.

"Queen Elizabeth has been keeping jewellery and gifts for years now, just in case William ever had a daughter," the source said. "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."