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It's industry standard for the bride's parents to pick up the tab for the big day. . . unless of course she's marrying a member of the royal family.

But Kate Middleton's mom and pop are breaking with Palace tradition and contributing a hefty six-figure sum for their daughter's April 29th wedding to Prince William, a senior aide tells Vanity Fair.

"It is something they absolutely wanted to do, and William graciously accepted," says the source.

Middleton's parents, Carole and Michael, worked for years in airline service. In 1987, they founded Party Pieces, a successful party supply company where Kate used to work.

The Middletons' money won't make much of dent in the cost of the festivities, however, the wedding will reportedly boast a price tag of more than $10 million.

"Kate's feet are still on the ground, largely because of Michael," a friend of the Middleton family tells the magazine. "He doesn't get too swept up in the grandeur of her new life, and Kate loves him for that."