Charles Koch Shares the Letter That Guides His Life

— -- Charles and David Koch are among the richest men in the world, amassing a multi-billion dollar empire and running the largest privately held company in America while largely staying out of the public eye.

When ABC News met Charles Koch at his company's headquarters in Wichita, Kansas, last week, he opened up to offer a rare glimpse into his personal story and the values that have informed his business career and political activities.

Koch, the author of the book "Good Profit," talked through a framed letter in his office left for him by his father, which outlined the approach he and his brothers should take when managing the family fortune left to them.

Koch reflected on how the letter has guided him in his business, and in a rare admission, Koch admitted his father would be "horrified" at the resulting feud that split most of his siblings apart.

Watch the ABC News digital original video above to hear Koch's story in his own words.