Mr Koch had stepped down from executive vice president of Koch Industries, a conglomerate which has an annual revenue of more than $100 billion, last year.

Charles Koch released a statement confirming his brother's passing on Friday, not specifying the cause but referencing his long struggle with cancer.

"Twenty-seven years ago, David was diagnosed with advanced prostate cancer and given a grim prognosis of a few years to live," the statement read. Read more