Hello, I've been looking for your folks since I saw your Query. I haven't been able to find Hugh on the Canadian side but his Death Record of 1939 confirms his father was Thomas Cahill and mother was Ellen Ryan.
Regards Agnes Ann(Grady) Cahill, Hugh's wife, born about 1863 in Guysborough Co.,NS, her parents were Tobias and Elizabeth(O'Gorman)Grady and they moved to Prince Edward Island just before the 1871 Census but you can see the family in the 1881 Census in PEI at the Census Page below.http://data2.collectionscanada.gc.ca/e/e325/e008114773.jpg
About three years later they leave for Duluth, Minn too.
There is a birth record for Richard James Grady, a brother to Agnes in NS Vital Stats (on line) in 1865.https://www.novascotiagenealogy.com/
Hope this info is useful. You will see on the 1881 Census that Tobias's first three children were born in NS, Guys Co.
It is also interesting that Hugh and Agnes named some of their children after her brothers and father Tobias.