He married Christina Sutherland (also Scottish), of Winnipeg in 1885; with her he had five children.
After Christina's death in 1907, he remarried English-born Emma Northfield.
After Emma's death in 1917, he married her sister, Ruth.
Bannerman came to Alberta, settling in Edmonton in 1882, and Calgary the year after.
With his brother, he was a flour and feed as well as liquor merchant.
A Protestant, he also served at a time as a City of Calgary alderman in the 1880s.
Though he was politically affiliated with the Conservative Party of Canada, he served as an Independent in the Legislative Assembly.
He was elected in 1894 to the Legislative Assembly of the Northwest Territories, and served until his defeat in 1898.