I am not sure where you got your dates from to come up with a marriage aged 13. Johan Rosie Douglas married Ovila Leduc on 31 Dec 1918 at Balloan Farm, Cawdor, Nairn. Johan was born on 18 January 1900 at Blackheath, Thurso, Caithness, Scotland and Ovila Pierre Leduc was born 14 Dec 1897 in Hawkesbury, Ontario
The Douglas families in Caithness are, mainly, settlers who were brought in from the Scottish Borders to look after the sheep once the glens had been 'cleared' of people. Thus, there is no common ancestor (in the Highlands).
There is no record of those who moved, so researching them is very difficult.
The more information you can give about the people you mention, the more chance there is of someone else connecting with your family.
Dates and places of births, deaths and marriages all help to place families.
Professions also help.
'My great-grandmother mother was a Douglas from Montrose' does not give many clues to follow up! But a bit of flesh on the bones makes further research possible. But if we are told who she married, what his profession was and where the children were baptised, then we can get to work.
Maybe it is time to update the information in your profile?