Thank you all, for the suggestions.
Turns out I had to go many generations back and many generations forward to uncover individuals with multiple parents, which each needed to be teased apart.
The tedious yet methodical search gave me a bonus ... my Data Error Reports now have zero critical errors. That's a first. And, it reinforces what many have said elsewhere on this FTM board ... do not trust the data in the Public Member Trees!! I speak from painful experience. :-)