Alongside Spencer, James had another brother, Michael. He died in 1999 at 22 after becoming the youngest Briton to reach the summit of Mount Everest. He disappeared on the way down, and his body was never recovered. In his memory, the family created the Michael Matthews Foundation, which builds schools to provide education for children in remote places.

James Matthews was educated at Uppingham School but did not go to college, instead initially following his father into motor sports. He then entered a finance career as a trader in London, before setting up Eden Rock in 2001.

Outside his day job, Mr. Matthews is a keen skier (so is Ms. Middleton), an avid tennis fan (Ms. Middleton is regularly spotted courtside at Wimbledon) and cyclist (the betrothed couple have competed together in a charity bike ride from London to Brighton). He owns a palatial house in Chelsea and a private jet.

How did they meet?

Ms. Middleton has some history with her modern-day Prince Charming. After meeting and becoming friends when the Middleton family went on vacation to Eden Rock more than a decade ago, the couple reportedly dated for a short period in 2012 before Ms. Middleton embarked on a three-year relationship with another financier, the stockbroker Nico Jackson. Ms. Middleton has also dated the banking heir J J Jardine Paterson and the former cricketer Alex Loudon, but a rumored romance with her sister’s brother-in-law, Prince Harry, seems largely fictional — wishful thinking by the British tabloids.