During the process of researching my McDonough family from Venango County, PA, I have run across the Cassidy family. My family has a few pictures of a Cassidy family. Also, my great grandmother's address book has the name of a Mr. & Mrs. Bernard Cassidy in PA.
Additionally, when I located the cemetery where my gg grandmother is buried, I found that her daughter is buried next to her. The headstone reads Sarah Cassidy, daughter of McDonough.
So, we now know that a McDonough married a Cassidy. If you have any further information please contact me. firstname.lastname@example.org
Thanks for your help