I have been sifting through Fred/John/etc's military records.
https://central.bac-lac.gc.ca/.item/?op=pdf&app=CEF&id=B9573-S048The last address for wife Betty [sic] as next of kin, was GPO Detroit, Michigan, and that was dated 24 Dec 1919.
However, Fred/John/etc was discharged in Jan 2020, to a hospital in Quebec, for treatment.
Betsy must have gone from Michigan to Quebec to be near him, and (assuming Peter is hers, as there are a LOT of Terry's), had the baby in Quebec. Perhaps there is a border crossing?