> Not entirely heritable? Or has no genetic correlation?

My understanding is that there is some genetic correlation but it's not a certainty; smart/rich parents can have dumbass kids and vice versa.

It's hard to quantify because a direct "IQ" measurement is fraught with issues and trying to measure by "success" has its own issues. If you've not met a lawyer/doctor/PhD that you'd put in the "dumbass" category, you probably haven't met many.