If the brother immigrated before 1911, you may be able to find him on the 1911 census.
You can try this site and see if you can find a possible brother.
http://automatedgenealogy.com1911 Census of Canada
Ontario
Thunder Bay and Rainy River
Fort William is Districts 20-29
The easiest way to search is to put Graham under surname search and then pick out ones that may match and then use the split view to look at original census pages. Census info gives age, country of birth, year of immigration, occupation and religion.
I would look for names that may fit in with a naming pattern that was very common in Scotland. Naming sons after father, grandfather, parents brothers.
Donald, age 28 and John , age 22 are two possible brothers but would take more researching to confirm.
If the brothers enlisted in the CEF, it may be possible to find them if the parents and addresses are listed as Next of Kin. You may have to wait for the 1921 census to get any real information.
If someone is able to find a marriage certificate tha may have the same prents listed would be another possible way to find the brother.
If you can provide the names of the parents, someone may work their magic and find something.