Billionaire industrialist David Koch, a driving force behind conglomerate Koch Industries who as one of the world's richest people became a major financier of conservative causes and political candidates, has died at age 79, his brother said on Friday.

Charles Koch, Koch Industries Inc's chairman, disclosed the death in a statement that touched on his younger brother's lengthy battle with prostate cancer and his philanthropic contributions to medical research, education and the arts.

"He will be greatly missed, but never forgotten," Koch said in a statement addressed to employees. "David was proud of the extraordinary work you all have done to make Koch Industries the successful company that it is today."