Thanks to Helen Smith, several of us doing Alexander research just recently became acquainted with the book on Alexander Alexander and his family. You will find it at: .
The book mentions that Agnes Kelly was born in Ireland and, I believe, mentions who her father was. It was written in the 1800s, fairly close to their time, and has a fair chance of being correct in that matter.
I urge both of you to visit our Alexander DNA web site, and investigate the possibility of being related to one of the lines mentioned there. And, Willis, I urge you as a male-line descendant from Alexander to get in contact with Roger (information at the site) and to participate in the DNA testing.