I am one of the Grandsons of Albert Stagg who is Robert C Stagg's youngest son.
My father remembers Jack Stagg although he passed away in 1969 and I was born in 1968.
Jack Stagg also had a ranch in the Kew area a little ways from the other Stagg ranches in the area. My father remembers helping him out on his ranch.
The other Stagg brothers that had ranches in the area was my grandfather Albert, his older brother Robert, Joe Stagg and of course Robert C Stagg
They split their time between Calgary at the family home and headed out to the ranches to work them.
Edward Stagg never had a ranch of his own but also I believe also helped Joe Fisher out back then. He moved up to Edmonton eventually and that is all that I know about Edward Stagg
From what I understand, Elizabeth Fisher/Stagg had 8 children although as she passed away in 1947, my father only has a limited memory of her. As far as I know, her children were Mary, Robert, Joseph, John, Jean, Kathleen, Harry and William (your father).
My father knew Jean Fisher (Blakley) fairly well as she lived on a ranch beside the Fisher ranch.
I found Elizabeth Fisher's gravestone as well as Joseph Fisher's in addition to one of their sons Robert Fisher in Union cementary in Calgary.
I am surprised that you or your father never met Robert Stagg jr (son of Robert C Stagg) as he used to split his time between living in Vancouver and Calgary. He did pass away in 1972 and I assume that by your username you were born in 1961.
Going back to the Staggs and the Fishers, Joe Fisher was born in 1844 and Robert C Stagg was born in 1845 in Carlisle England. They were both sons of farmers and lived beside each other so it is no wonder that they were friends from childhood.
If you get to the Stagg/Fisher Gravesite in Union Cementary in Calgary, there is a large marker with Stagg on one side and Fisher on the other side. This shows how their lives back then were together