<p>Not long after the death of his father, whose heart gave out suddenly in November 1967, Charles Koch, then in his early 30s, discovered a letter his father had written when his four sons were small. "My dear boys," it began when you are 21, you will receive what now seems to be a large sum of money. It may either be a blessing or a curse." "Above all," he cautioned, "be kind and generous to one another."<br>In the ensuing decades, Fred''s legacy became a blessing and a curse. <br><br>Two of his sons, Charles and David, joined forces to build Koch Industries, one of the largest private corporations in the world. But they ended up in an epic feud with brothers Bill and Frederick that spanned nearly two decades, tearing the family apart-and nearly Koch Industries along with it. Bill would start his own energy company and attain a modicum of fame as a litigious wine-collector and yachtsman (he likened winning The America''s Cup in 1992 to the ecstasy of "10,000 orgasms.") After being ma