Paul Allen
Seattle Seahawks owner Paul Allen walks across the field before a football game between the Detroit Lions and the Seattle Seahawks at CenturyLink Field in Seattle, Washington, Oct. 5, 2015. Getty Images/Stephen Brashear

Paul Allen, the co-founder of Microsoft, died Monday at the age of 65 from complications of non-Hodgkin’s lymphoma, his family said in a statement. The investor, entrepreneur and philanthropist's death came just two weeks after Allen said he was being treated for the disease.

His sister, Jody Allen, released the following statement from his family: “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."

She continued: "Paul’s family and friends were blessed to experience his wit, warmth, his generosity and deep concern. For all the demands on his schedule, there was always time for family and friends. At this time of loss and grief for us — and so many others — we are profoundly grateful for the care and concern he demonstrated every day.”

Allen, who never married or had children, is survived by his sister Jody.

He died in Seattle, Washington, his family said through Allen's company, Vulcan Inc. Allen had battled the disease in 2009 and announced earlier this month that his lymphoma had returned.

He said in a statement at the time that he had started treatment and that he "plan[ned] on fighting this aggressively... A lot has happened in medicine since I overcame this disease in 2009." "My doctors are optimistic that I will see good results from the latest therapies, as am I," he added.

Allen founded Microsoft (MSFT) with Bill Gates in 1975 but left the company in 1982 after he was diagnosed with Hodgkin's disease.

"I am heartbroken by the passing of one of my oldest and dearest friends, Paul Allen," Microsoft founder Bill Gates said in a statement Monday. "Paul was a true partner and dear friend. Personal computing would not have existed without him."

Microsoft CEO Satya Nadella also released a statement that reads, "Paul Allen's contributions to our company, our industry and to our community are indispensable. As co-founder of Microsoft, in his own quiet and persistent way, he created magical products, experiences and institutions, and in doing so, he changed the world. I have learned so much from him — his inquisitiveness, curiosity and push for high standards is something that will continue to inspire me and all of us at Microsoft. Our hearts are with Paul's family and loved ones. Rest in peace."

The technologist, who according to Forbes was worth $20.3 billion at the time of his death, donated more than $2 billion to charity. In 2014, he pledged at least $100 million to help fight the Ebola virus. In 2017, he pledged $30 million to house Seattle's homeless.

Former Microsoft CEO Steve Ballmer called Allen a "truly wonderful, bright and inspiring person -- and a great friend," on Twitter, adding "I will miss him."

"Our industry has lost a pioneer and our world has lost a force for good. We send our deepest condolences to Paul’s friends, the Allen family and everyone at Microsoft," Apple CEO Tim Cook wrote on Twitter.

Allen was also the owner of the Portland Trail Blazers and the Seattle Seahawks.