In the study mentioned in original article seems to account for this by comparing elite and near-elite athletes, and having found they had the same number of si

In the study mentioned in original article seems to account for this by comparing elite and near-elite athletes, and having found they had the same number of siblings. "On average, the two groups had the same number of total siblings. What mattered was whether those siblings were younger or older. The elite athletes had 1.04 older siblings on average; nonelite athletes had only 0.61." I think this ratio is greater than what you find in the general population analysis.