I noticed that you indicate that John Campbell, Peter's father may have had a sister Mary. This I did not find in my research. Do you have any more info on her? Also do you have a date of death for John. Traces of him seem to have disappeared after the 1891 census. Any other records of his other family, with Ann McGill,after 1911 also seemed to have dried up.
You mention a Campbell Book which I am unaware of but would be extremely interested in.
Please e-mail me at firstname.lastname@example.org
and perhaps we could compare notes.
The Lothian family also were from what is known as the Ridge and bordered on Prescott/ Glengarry. I had a 1st cousin who married a Lothian. They called their only son Peter who died at age 8 or 9
Thanks Bill Campbell