The royal household is expanding yet again as Kensington Palace announces the future arrival of Kate Middleton and Prince William's third child. It's very early days as of yet, but the Duchess has been exceedinly unwell - as she has come to expect with her pregnancies.

The Duke and Duchess of Cambridge at a public engagement at Kensington Palace's White GardenThe Duke and Duchess of Cambridge at a public engagement at Kensington Palace's White Garden

Catharine, the Duchess of Cambridge is actually less than 12 weeks pregnant, but given that she has been struggling with severe morning sickness regularly, she has been forced to pull out of a recent public appearance. The Palace decided to announce their happy news early, so that any future absences aren't met with worried speculation.

'Their Royal Highnesses the Duke and Duchess of Cambridge are very pleased to announce that the Duchess of Cambridge is expecting their third child', Kensington Palace announced in a statement. 'The Queen and members of both families are delighted with the news. As with her previous two pregnancies, the Duchess is suffering from Hyperemesis Gravidarum. Her Royal Highness will no longer carry out her planned engagement at the Hornsey Road Children's Centre in London today. The Duchess is being cared for at Kensington Palace.'

William and Kate's new arrival will join 4-year-old Prince George - the third in line to the throne - and 2-year-old Princess Charlotte. Kate was diagnosed with Hyperemesis gravidarum in her first pregnancy, and was forced to undergo hospital treatment. It appears she has learnt how to manage her delicate condition, however, as no hospital stays have been required since for that issue - and it's certainly not putting her off having more children.

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Her brother-in-law Prince Harry was certainly thrilled by the news of another niece or nephew, telling the Telegraph that he felt 'Fantastic. Great. Very, very happy'. Plus, it seems that Kate's condition hasn't been serious enough to cause the whole family worry, as he revealed: 'I haven't seen her for a while but I think she's ok.'