Barclay died unexpectedly after a short illness, the Telegraph reported. That newspaper and other investments, including the five-star Ritz Hotel in London’s Mayfair district, put David and Frederick among the top ranks of the U.K.’s rich and powerful.

The twins forged reputations as stealthy buyers who rarely turned to public markets or investment bankers to finance deals for their closely guarded business empire. However, the billionaire family was thrust into the spotlight last year through a legal battle that revealed Frederick was being secretly recorded by one of David’s sons at the Ritz prior to its sale.

Read more: Bugging the Ritz, Private Investigators and Billionaires at War

Born 10 minutes apart from Frederick to Scottish parents, David spent his early days in a west London household so close to a railroad that trains rumbling by would rattle the windows.

After leaving school, the brothers started their careers in the accounts department of General Electric Co., according to “The Twin Enigma,” a 2016 book by Vivienne Lewin. They teamed up in the 1960s to turn old boarding houses into hotels, and moved into breweries and casinos, marking the beginning of their business empire.

The brothers rose to prominence in the U.K. through the media and real estate industry. In 1995, they bought the Ritz, and also acquired a stake in the entity that owned London luxury landmarks Claridge’s, the Berkeley and the Connaught. They sold that stake in 2015 after a protracted fight to control the business.

The Barclays paid 2.3 million pounds in 1993 for the English Channel island of Brecqhou for a family compound. They erected a mock-Gothic castle, complete with almost 100 rooms, turrets and a helipad.

In their initial foray into publishing in 1992, David and his brother purchased The European newspaper, which had been started by publisher Robert Maxwell, who had died suddenly. They turned it into a high-end business tabloid, though it closed a few years later. They also acquired the Scotsman newspaper and, in 2004, bought the Telegraph Group which included the Daily Telegraph, the Sunday Telegraph and the Spectator.

Even as their holdings grew, the business remained a family affair, with David’s sons Aidan and Howard increasingly running matters. David had two other sons, Duncan and Alistair.

”We were twins from the beginning until the end,” Frederick said in the statement. “He was the right hand to my left and I was his left hand to his right. We’ll meet again.”