David Koch, the billionaire businessman who built a conservative political empire with his brother Charles, died Friday at age 79, according to Koch Industries.

The company said his death comes "after many years of fighting various illnesses."

In a statement, Charles Koch announced his brother's death "with a heavy heart," praising 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," the statement said. "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 brothers, who ran a family oil, chemical and textile conglomerate, are known for the conservative empire they funded aimed at promoting conservative policies. Among the efforts was the Americans for Prosperity Foundation, which has pumped millions into conservative causes. They also were once shareholders at the libertarian Cato Institute.

David Koch also made a bid as a Libertarian Party vice presidential candidate in 1980.

According to the author of the book "Kochland: The Secret History of Koch Industries and Corporate Power in America," Christopher Leonard, "they have played an unrivaled role in the issue of climate change" starting in 1991.

In an interview with Fortune in 2016, David Koch said he does believe there is evidence that greenhouse gases are contributing to "warming," but "I don’t think anybody knows how much. I don’t think science is settled."

Koch retired from his position as executive vice president of Koch Industries and was named director emeritus after reporting unspecified health issues in 2018. At the time, Charles Koch said in a statement to Koch employees that David Koch’s health had been decline since 2016.

Koch also stepped down from the board of the Americans for Prosperity, a libertarian political advocacy group, in 2018.

Secretary of State Mike Pompeo called Koch "a compassionate philanthropist, successful businessman, and a proud American."

This story will be updated.