Quote Originally Posted by Messenger View Post
If better stallions are mostly from better horses (some exceptions of course and many who are probably never given a chance for commercial reasons) and better horses are mostly from better families - isn't that a correlation of a sort?
Sorta. But if the maternal family has significance, then stallions from these families must do better than otherwise comparable stallions and that is on paper a different correlation.

Btw, if maternal family matter, one could also expect stallions to perform better with mares from certain families. Such statistics are available and show clearly that there is no such relation in general.