The Duke and Duchess of Cambridge, Prince William and Kate Middleton, are no strangers to lofty parties lately, with Queen Elizabeth's recent Diamond Jubilee extravaganza, as well as their own celebrated nuptials last April, and now the most famous couple in the world is gearing up to celebrate the milestone of William's 30th birthday.

Maybe Kate and William have been exhausted by all the excitement, however — it turns out they are having a low-key evening for William's 30th. "Kate had been planning a small dinner party with their friends and some family," a source told Us Weekly. The party will be at Prince Charles' countryside house.

Furthermore, William isn't even using the occasion as an excuse to take a vacation. "William is working as usual during his birthday week," said an aide from the palace. "Tonight he will have a private celebration with family and friends," taking a brief break before returning to the Royal Air Force base in Gloucestershire, where he is undergoing training.

The low-key night is typical of William and Kate's relationship, who like to take it easy amidst the glitz and glamor of their public lives. On a regular evening, "Kate will cook his favorite dinners after he gets home from work … or she'll order movies on Amazon for them to watch on the couch."

For more on William and Kate:

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Kate Middleton's Valentine's Day Charity Tour

Kate Middleton Accompanies Queen On Diamond Jubilee Tour In Leicester

Kate Middleton Takes Tea With Queen Elizabeth, Camilla For Inaugural Diamond Jubilee Event

Kate Middleton Flies Solo, William Away In The Falklands

Family Ties: Kate Middleton Related To Jane Austen

Kate Middleton Top International Best Dressed List

Kate Middleton’s Wedding Dress To Be Displayed