Just glancing quickly through the top 15 richest Americans: Bill Gates' parents were a lawyer and bank director, Buffet's dad was a congressman, the Koch brothers are the sons of an oil baron, the Walton kids...enough said, Bloomberg's dad was a real estate agent, Jeff Bezos' family owned a 25k acre ranch in Texas, Larry Page's parents were both college professors, Sergey Brin's dad is a college professor and his mother works at NASA, and Forrest Mars is the grandson of the founder of Mars Corp.
There's, like, one person of the list [Sheldon Adelson] who actually grew up poor.