Is Kate Middleton having twins?

Following news that Kate Middleton is expecting her third baby, Australian magazine New Idea is claiming that the Duchess of Cambridge is in fact pregnant with twins.

The magazine has reported that a "trusted high-ranking palace aide" has confirmed William and Kate, both 35, are preparing for the arrival of not one but two little bundles of joy.

If the magazine's claim is correct, it will be the first set of twins in the Royal family since the 15th century.

But British bookmakers are doubtful as bets are currently at 20 to one that two babies are on the way for the Cambridges.

Kate's pregnancy news came early after falling ill with extreme Hyperemesis Gravidarum, a rare form of morning sickness that the Duchess also suffered in her previous pregnancies.

The Royal mother to George, 4, and Charlotte, 2, has been so unwell that Kensington Palace made the announcement after the Duchess was forced to cancel a public engagement.

Kate was also unable to accompany George to his first day of school at Thomas's Battersea last week.

William has described Kate's third pregnancy as "the best news he's had all year".

This article was first published on nzherald.co.nz and is reproduced here with permission.