Paul Allen, who founded Microsoft with Bill Gates in the 1970s and later went on to become an investor, philanthropist and sports team owner, died Monday after his latest battle with cancer at age 65.
"My brother was a remarkable individual on every level. While most knew Paul Allen as a technologist and philanthropist, for us he was a much loved brother and uncle, and an exceptional friend," Allen's sister Jody said in a statement announcing his death.
In recent years, Allen was known as the owner of the NFL's Seattle Seahawks and the NBA's Portland Trail Blazers, and part owner of the Major League Soccer team the Seattle Sounders, along with a variety of business and charitable ventures.
One of the world's wealthiest billionaires, Allen also founded Stratolaunch Systems, which built the world's largest plane designed as a colossal rocket-launching aircraft touted as the future of space travel. The craft was on track for its first launch demonstration as early as 2019.
Allen died just two weeks after publicly revealing that non-Hodgkin's lymphoma he fought into remission nine years ago had returned. The incurable cancer affects white blood cells.
He never married and had no children.
Allen was a high school classmate of Gates in Seattle, and later, while working as a computer programmer, persuaded his friend to drop out of Harvard to create Microsoft, which became the world's most valuable company in the 1990s.
A "heartbroken" Gates remembered Allen as "one of my oldest and dearest friends."
"Personal computing would not have existed without him," Gates added.
"He was fond of saying, 'If it has the potential to do good, then we should do it.' That's the kind of person he was."
Allen had left Microsoft by 1983 for health reasons but held on to shares that made up the bulk of his fortune, estimated at some $20 billion.
"All of us who had the honor of working with Paul feel inexpressible loss today," said a statement by Vulcan, the investment firm that managed his operations.
"He possessed a remarkable intellect and a passion to solve some of the world's most difficult problems, with the conviction that creative thinking and new approaches could make profound and lasting impact."
Microsoft said Allen's "contributions to our company, our industry and to our community are indispensable." He invested $100 million to found the Allen Institute for Brain Science in 2003.