6. (165) Blair Parry-Okeden, $8.92 billion
Parry-Okeden, 67, is the daughter of the late billionaire Barbara Cox Anthony and the grandaughter of the late James M. Cox. James Cox, a 1920 Democratic presidential candidate, founded a chain of newspapers in 1898 that grew into the media company Cox Enterprises, the third-largest cable operator in the U.S. Parry-Okeden inherited a 25 percent share of the company, which had sales of $20.4 billion in 2017. Known for keeping a low profile, she moved to Australia in the 1970s and is active in philanthropy.