Conservative billionaire David Koch, who became a household name through his political lobbying efforts and the company he created with his older brother, Charles, has died. He was 79.

Charles Koch, the CEO of the family’s industrial conglomerate Koch Industries, announced the death 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,” the elder Koch said in a statement. The statement did not cite a cause of death but noted David Koch’s decades-old battle with prostate cancer.

Koch cited health reasons when he stepped away from his company a few years ago. Sources close to the family have said he had been in declining health in recent weeks.