I see there is some further info on the real Alex McRae here.
He enlisted the same day in Pincher Creek with No.118088 Kenneth McRae, apparently no relation, but who knows? Kenneth went on to become a CSM with the DCM, MM and bar, DoW, 29th of Sept. 1918. Friends and relations often enlisted together and Pincher Creek was little more than a village then. Probably they went there together to get into the 13 CMR rather than some other unit.
There's no trace of 118087 Alex McRae in the usual records online, except that he was probably living in Toronto in 1912 and working at a firm of plumbers and gas fitters. This would probably be when he was in the 48th Highlanders who are a Toronto militia regiment to this day.
Looks like he may have been concealing his real date and place of birth. Not so uncommon in those days when family problems were to be hidden at all costs.
There's practically nothing on his brother Angus either and no sign of his parents either.