I am researching the exact same people that you are in the McKibben line. I wonder if it's possible that John D. McKibben's 2nd wife, Frankey (Frances), could have been the Alexander that we keep hearing about.(?)
The reason that I suggest that is because several people with the surname of Alexander are named in Frankey McKibben's will dated 11 Aug 1801.
In the will, she mentions Matilda Alexander, Dorcas Alexander, and the sole executor is a George Alexander.
Coincidence?? Maybe. It's just a theory. Maybe we can poke around and see if we can find a Frances Alexander Laird McKibben. We know she married a Laird first because she mentions her son, Samuel Laird, in her will as well.