I'd be curious to see if the rate of "exceptional" children is higher for "exceptional" families than "unexceptional" families since by definition it's going to be far from the norm regardless. But the rate could still be 2x or 3x (I don't think it is, but it's a possibility). There's a lot of focus on the exceptional but I think where having a very rich or wealthy family helps is less in a much bigger upside, which certainly exists in some degree, but in a much higher floor.

If you are born into a single-income, lower-middle class family, your floor is poverty and even literally starving to death. If you're born into a family of two high-income individuals, the odds of you living your adult life in poverty are vanishingly small and your floor is probably something closer to a ho-hum middle/upper-middle life. If you're born into a family where one of your parents is the CEO of a publicly traded company and makes tens of millions a year, your floor is probably a $150k/yr lower management job in some sector-adjacent company that your parents had to call in a bunch of favors to get you.

It's not so much that coming from an exceptional family increases the "genetic" odds of exceptionality, but it provides safety and security that allows you to take risks someone waiting tables at night to pay for college wouldn't be able to, which coupled with the natural contacts and associations you'll have, gives you a huge advantage.