https://www.mercurynews.com/2019/08/23/david-koch-libertarian-activist-and-billionaire-philanthropist-dies-at-79/

David Koch, brother of Charles Koch and one of the owners of Koch Industries, the second-largest private company in the U.S., has died at 79.

According to the New York Times, Charles Koch announced the news of his brother’s death in a statement. Though he did not attribute to David’s death to a particular cause, he mentioned that David had battled prostate cancer in the past.