The Virgin tycoon, 75, and his wife were wed in 1989 when their two children, Holly and Sam, were eight and four. The couple now have three grandchildren.
The pair met in 1976 at The Manor, a live-in recording studio for the company, three years after Mike Oldfield's Tubular Bells launched Virgin into the public consciousness.
Announcing the 80-year-old's death on social media, the Virgin boss wrote: 'Heartbroken to share that Joan, my wife and partner for 50 years, has passed away..