The 1881 Census referred to above, states Alexander and his wife were born in Scotland, as were the first four of the children listed - therefore their marriage was likely in Scotland, not Canada or US.
'Alspet' is undoubtedly "Elspet" - a common Scottish female name and a form of "Elizabeth".
The 1891 Census (linked in the prior thread listed), reiterates:
1891 Southampton, Bruce North, Ontario½
Alexander DUNBAR 55, b Scotland
Elizabeth 55, b Scotland
Bella 22, b Scotland
Jessie 18, b Ontario
William 15, b Ontario
son James is 'next.door' ½
James DUNBAR 26, b Scotland (abt 1865)
Ann 26, b Ontario
Olive 3, b Ontario
Ellen 1, b Ontario
James died in 1947:James Asher DUNBAR, age 81 years, widowed,
B 14 March 1866 Lockhill, Scotland
D 24 Aug 1947 Port Arthur, Thunder Bay, Ontario, Canada
Father: Alexander DUNBAR
Mother: maiden name SHAND
Spouse: Annie OLIVER
In Municipality 44 years, In Province & in Canada 77 years
His birth:James Asher Dunbar, born 14 Mar 1866
Urquhart, Morayshire, Scotland
Father: Alexander Dunbar
Mother: Elspet Shand
His parents married:Alexr DUNDAR and Elspet SHAND on 14 Nov 1857, Urquhart, Morayshire Scotland
This marriage cert, through Scotlands People website, should give the names of both sets of parents.
Their headstone in Southampton, Bruce County, Ontario:https://www.findagrave.com/memorial/175858192/elspet-dunbarInterestingly, when James married Annie OLIVER in 1888, In Port Elgin, Ontario he gave his place of birth as Aberdeenshire - and Lockhill (the birthplace on his death record) is in Aberdeenshire. His sister Bella was a witness, and he gave parents names as Alexander Dunbar and Elsie Dunbar.
Alexander and Elspeth were in Canada in time for son Joseph Reach DUNBAR's birth on 22 Aug 1870, in Halton, Ontario. Parents: Alexander DUNBAR and Elspit SHAND. Informant, Joseph Reach, Postmaster, Bronte. Alexander's occupation: Waggon Maker.
Cheers
AMBLY