Exactly. Families share more than genetics.

I once heard a radio spot where a woman spoke about herself and her sister's illustrious pole-vaulting career. She scoffed at the idea that she had taken up pole-vaulting because her older sister did it, and said "obviously" they both had pole-vaulting genes

I wasn't aware anyone doubted that there are genes that convey athletic abilities

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?

I bet there are many that we take for granted. My first thought was social class; that's environmental and it's possible they all had this in common.

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.

The poster wondered what environmental factors these family members may have shared, social class is definitely one such factor.

Are you arguing that may not be the case? I think you would need more information about the poster's family to make that assertion.

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.