Carole Middleton has been described as a "mastermind" in her daughter Pippa's romance with fiancé, James Matthews.
Mrs Middleton, whose other daughter is the Duchess of Cambridge, is said to be thrilled that the couple are marrying after almost a decade of speculation surrounding their relationship.
One friend said Miss Middleton's mother confided several years ago that she hoped they would give it a serious go. "This is something she has hoped for for quite some time," said one associate. "She appears to be something of a mastermind in making this happen."
Mr Matthews, 40, a hedge fund manager, reportedly proposed after arranging a meeting with Mrs Middleton, undoubtedly seeking permission for her daughter's hand.
He is said to have been patiently pursuing his bride-to-be for 10 years, with the bond to his future mother-in-law secured several years ago when both families holidayed on St Barts in the Caribbean.
Having earned millions from Eden Rock Capital Management, named after his parents' Caribbean hotel, Mr Matthews has wooed Miss Middleton with a £250,000 art deco engagement ring featuring a three-carat Asscher-cut diamond and has given her a £14,500 Cartier Ballon Bleu watch.
Miss Middleton, 32, has said she "couldn't be happier" since he surprised her with the proposal in the Lake District.
They may marry in Bucklebury, the Berkshire home of her parents. However, Miss Middleton loves shooting in Scotland so may have her heart set on a reception in the Highlands where the Matthews family owns a 10,000-acre estate.
The Duchess of Cambridge is expected to take the role her sister played at the Royal wedding as maid of honour, while Prince George and Princess Charlotte may be page boy and flower girl.