I don't see a link to this actual study, only the TEDS study (was it actually parts of the TEDS study, or just using the same data?) But my first question is if

I don't see a link to this actual study, only the TEDS study (was it actually parts of the TEDS study, or just using the same data?) But my first question is if they've considered if really the correlation is coming from closely related variables other than just age: - Father's who start a family later vs father's who start a family early but have additional children later. - Children who are more likely to have multiple older siblings.