One aspect that isn't mentioned that I think probably has a huge impact: money. Not talking about whether the older siblings' career makes money that's used fo

One aspect that isn't mentioned that I think probably has a huge impact: money. Not talking about whether the older siblings' career makes money that's used for the younger, although that might be the case as well. Instead, by the time the younger starts the parents probably have more of it. Given that for academic success money is a huge factor, I'd wager it's in sports as well.