In the Old Testament canon, there are fewer Big Dogs than Adam, the first human. We know that he is the husband of Eve, and the father of Abel & Cain. He was also the father of Seth, about whom I knew nothing. And I guess there were other children as well, though we don't have their names.
The source I was using mentioned that Adam and Eve taught Seth how to resist the temptation of evil. I suppose experience counts for something.
There were lots of other saints to choose from. Blessed Bartholomew dal Monte would have been a fine pick. Sharbel the Maronite might have also -- his post-mortem miracles were really extraordinary. But it just seemed disrespectful not to give Adam this post, even if he is somewhat less well attested.