Donald Canmore should not be confused with Donald Ban, Canmore's historical brother who became Donald III of Scotland.
Real World Background
In the real world, one of Canmore's many sons was named Donald (or Domnall in Scottish). According to one account, Donald son of Canmore died in 1085. We do not yet know enough about the Donald Canmore of the Gargoyles Universe to know if he is this historical figure, but it is likely that they are the same person.