There's a difference in degree here too though: there's a massive difference between "son of a lawyer" and "son of a central committee member". Gates is considered one of the more privileged billionaires, because his mother was on the board of directors for United Way and his father was a prominent lawyer. That seems like a crack down from his parents being President or in the Cabinet.
It also ignores counterexamples like Steve Jobs (from a working class, blue collar family), Larry Ellison (Jewish immigrants who worked as modest government employees) or Larry Page and Sergey Brin (children of professors).
Hm well professor is not exactly middle class either... Actually children of professors are probably the best prepared to make a great career more than anyone else. Parents with connections, lots of knowledge and more time than people working in the industry - that's the perfect mix. I know a few sons of professors, they just surf through life.
Buffet's father wasn't a politician until after Buffet was rich. If anything, in western countries it's easier to become a government official because you're related to someone rich than it is to get rich because you're the kid of a government official.
Connections help. In a totalitarian society they help more.
The only thing that stops the situation from being much worse is term limits.