Michael and Carole Middleton will be paying towards their daughter's wedding to Prince William next April.
The self-made millionaires have insisted on a contribution to the royal event, and are said to want to pay for a specific aspect of the wedding, like the honeymoon or Kate's dress, rather than make an overall, more "impersonal" contribution.
According to a royal source: "Prince William and Catherine's intention right from the outset has been to make sure that the Middleton family are as tied into the arrangements as possible.
"It was a very kind offer on their part and it has been kindly received at this end. We don’t expect their contribution to be a percentage of the final bill, which would be quite impersonal; it's much more likely that they will offer to pay for something specific."
Experts are already making predictions about the cost of the big day, the majority of which will be paid by the Queen and Prince Charles. The total is expected to top £10 million, including policing and security which will funded by the tax payer.
It has been estimated that Kate's dress will cost at least £40,000 while the cake, or cakes, to feed Westminster's 2,000 guests could reach anything between £10,000 and £50,000. Flowers to fill the abbey and Buckingham Palace are expected to total between £200,000 and £500,000.
Speaking about the royal family's decision to fund the big day, William's private secretary, Jamie Lowther-Pinkerton, - in overall charge of the wedding – said: "All parties involved, not least Prince William and Miss Middleton, want to ensure that a balance is struck between an enjoyable day and the current economic situation.
"To that end, the Royal family and the Middleton family will pay for the wedding – the church service, music, flowers, decoration, reception and honeymoon.
"The Royal family are drawing on the precedent of the Queen and Prince Philip's wedding in 1947 and the wedding of the Prince and Princess of Wales in 1981."