Billionaire David Koch has died aged 79.

Mr Koch was a major donor to conservative causes and educational groups.

Together with his older brother, Charles, the Kochs were best known for a vast political network they built that became popularly known as the “Kochtopus” for its far-reaching tentacles in support of conservative causes.

The brothers founded the anti-tax, small government group Americans For Prosperity.

David Koch
David Koch (Phelan M. Ebenhack/AP)

Charles Koch remembered his brother for “his giant personality and passion for life” and said he will be “greatly missed, but never forgotten”.

He said his brother was diagnosed with advanced prostate cancer 27 years ago but liked to say that “brilliant doctors, state-of-the-art medications and his own stubbornness kept the cancer at bay”.

Charles Koch said his brother “was able to touch so many more lives as a result” in the ensuing years.

Mr Koch was an engineer trained at MIT.

He joined Koch Industries in 1970 and served on its board.

He was chief executive officer of Koch Chemical Technology Group, a Koch subsidiary.

Charles and David Koch, each with an estimated net worth of 31 billion US dollars, tied in fourth place in 2012 on Forbes 500 list of the nation’s richest men.