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Angelina Jolie's 37th birthday bash was anything but a blowout.

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The understated and intimate affair took place on June 4, 2012, at the Jolie-Pitt family's rented mansion in Surrey, England, a source confirms to Us Weekly exclusively. (The stars are shelling out $24,000 a month to rent the posh Wentworth Estate.)

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"It was a very small bash -- just the family at home. They didn't go out or do anything," according to the source. "Just a simple one at home with a cake. No frills, but they're all really happy at the moment. Everyone's doing good."

No word yet on what Brad Pitt bought his bride-to-be for her special day -- but hopefully it's something extravagant, as Jolie purchased a waterfall for the "Moneyball" star's 48th birthday and Christmas presents in December 2011.

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Jolie is currently in England prepping for her role in Disney's "Maleficent," based on the villain from Sleeping Beauty. Pitt, meanwhile, will return to Budapest around June 20 to begin two weeks of reshoots for "World War Z." While Pitt is away filming, an insider tells Us, "the kids will stay back in the UK with Angelina."

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Given their busy filming schedules, it's also unlikely that Pitt and Jolie will tie the knot by year's end. "We actually, really and truly, have no date," Pitt -- father to Maddox, 10, Pax 8, Zahara, 7, Shiloh, 5, and twins Vivienne and Knox, 3 -- revealed at the Cannes Film Festival in May. "We're still hoping that we can figure out marriage equality in the states before [we exchange vows]."