What aspect of the environment was shared across 3 generations of uncles and cousins, geographically separated, many of whom didn't even know each other?
Well can you make any sort of case for a causal arrow to support your dismissal? Because there is a case for a causal arrow in your dismissal target, given the article we're commenting on. The bar has been raised for "we said, they said" so you'll have to try a bit harder than assertively blaming environment.
No, I'm saying that there is a demonstrated causal arrow from genes to intelligence. The evidence is less clear on the causality of social class and intelligence, however, so simply asserting it as a causative factor is not an effective rebuttal.
I obviously don't know the people concerned - but they presumably shared knowledge of the careers of their relatives? Peer pressure in families can be very strong even when it is indirect.