8. (209) Victoria Mars, $7.62 billion
Like her sisters, Victoria Mars started her career working at the Mars company. She has served on the company's board of directors since 2006 and served as company chairman in 2014. A graduate of Yale University, she earned an MBA from the University of Pennsylvania's Wharton School of Business. She also attended the Foxcroft college-preparatory boarding school in Middleburg, Va., and now is a member of the school's board of trustees.