Ages: Charles, 75; David, 70
Occupations: Charles, chairman and CEO of Koch Industries; David, executive VP of Koch Industries
Previous TIME 100 appearances: 1
The longtime backers of libertarian causes became infamous in liberal circles after a searing New Yorker exposé revealed their vast network of influence. Owners of a private conglomerate based in Wichita, Kans., the billionaire Koch (pronounced Coke) brothers have showered cash on conservative candidates, free-market think tanks and pro-business advocacy groups. Their largesse has helped train Tea Party activists and rallied opposition to key Obama Administration bills like health care reform and cap and trade. Buoyed by their success, they're reportedly ready to shell out nearly $100 million to spread their message in 2012.