Charles is the steady, driven one. He's grounded in the Kansas soil of their birth.
David is his outgoing younger brother. He's a New Yorker now, and pronounces himself forever changed by a near-death experience.
William is David's free-spirited twin, a self-described contrarian whose pursuits beyond business include sailing, collecting things and suing people (his brothers included).
And then there's the oldest, Frederick, who's as likely to turn up in Monte Carlo as at his apartment on New York's Fifth Avenue and doesn't have much to do with the rest of the lot.
They're all fabulously wealthy, all donate lavishly to charity, all tall — Frederick is the shortest at 6-foot-2 — and all are prostate cancer survivors.
Two of them, Charles and David, have defined the public notion what it means to be a "Koch brother."
In the eyes of the political establishment, it's the willingness to freely spend their awesome wealth in the pursuit of a smaller, more limited government. Among the executive set, it's their success at turning Koch Industries into a corporate behemoth whose reach extends into every corner of American life — toilet paper to jet fuel, fertilizer to cattle.
Among Democrats? Well, it's the idea that success at business allowed them to advance a political agenda that is designed to benefit those businesses.
The other two brothers — known in the family as Bill and Freddie — cut their ties to the family business decades ago and don't show the same passion as Charles and David to change the world. One of them, if you can believe it, has even given money to Hillary Rodham Clinton. (That would be Bill.)
As Bill sizes up his siblings during an interview with The Associated Press: "David and I like off-color jokes, Freddie likes more sophisticated jokes." Charles? "Charles likes golf."
Let's start with Charles and David, the two in sync on business and politics who most people think of when referring to the "Koch brothers." To even pair these two together risks missing their differences, of both geography and style.
Charles is the white-haired alpha male at the helm of Koch Industries. Midwestern through and through, the 78-year-old still walks up four flights of stairs to work at Koch headquarters in Wichita, Kansas, each morning and eats his lunch in the company cafeteria.
After building Koch Industries into the nation's second-largest private company, he turned his business philosophy into a book, "The Science of Success," drawing on — take a breath here — "economics, ethics, social philosophy, psychology, sociology, biology, anthropology, management, epistemology and the philosophy of science."