Conservative billionaire David Koch has died at the age of 79.

Last year, Koch stepped down from Koch Industries and his influential political network Americans for Prosperity Foundation, citing his declining health.

Koch’s 83-year-old brother Charles confirmed the death in a statement Friday.

“It is with a heavy heart that I announce the passing of my brother David. Anyone who worked with David surely experienced his giant personality and passion for life. Twenty-seven years ago, David was diagnosed with advanced prostate cancer and given a grim prognosis of a few years to live. David liked to say that a combination of brilliant doctors, state-of-the-art medications and his own stubbornness kept the cancer at bay. We can all be grateful that it did, because he was able to touch so many more lives as a result,” the statement said.

Koch leaves behind his wife, Julia, and their three children, David Koch Jr., Mary Julia Koch, and John Mark Koch.

“While we mourn the loss of our hero, we remember his iconic laughter, insatiable curiosity, and gentle heart. His stories of childhood adventures enlivened our family dinners; his endless knowledge rendered him our ‘walking Google.’ His sensitive heart had him shed a tear at the beauty of his daughter’s ballet, and beam with pride when his son beat him at chess. We will miss the fifth link in our family,” his wife said in a statement.

The brothers used their wealth to push for smaller government and traditionally supported Republican candidates and causes.

Koch had resisted resigning despite being in declining health for several years, but Charles forced him out of the family business, the New Yorker reported in 2018. Koch had served as vice president of Koch Industries before his retirement.

More details about Koch’s health were not provided.

Koch was also known for his philanthropy, donating millions to cancer research. He was a board member for the Prostate Cancer Foundation and donated $100 million to build the David H. Koch Center at New York Presbyterian Hospital. He also contributed $100 million to the New York State Theater at Lincoln Center, which is now named the David H. Koch Theater, $65 million to the Metropolitan Museum of Art, and $1 million to the Sept. 11 Memorial Museum.

Koch once ran for vice president on the Libertarian Party’s ticket with nominee Ed Clark. Their campaign ran on abolishing welfare, minimum wage laws, corporate taxes, and Social Security. The pair received only 1% support in the 1980 election, where Ronald Reagan defeated President Jimmy Carter.

The brothers’ political network did not support President Trump in the 2016 election and does not plan on backing his reelection efforts in 2020.