Hi Apollo,
I had a wee look in the 1881 Cencus to see if I could find a William Gourlay born c1863 (+/- 5 years). There were a total of 14 in the Highlands Region but without knowing any more about him, it could be any of them.
I looked for Mary Ann Ross, thinking she was maybe born in Stirlingshire, again c1863 +/- 5 years and found only one:
Here's the family:
Dwelling: 31 Glencoe Rd
Census Place: Stirling, Stirling, Scotland
George ROSS, age 49, Birthplace: Foss, Perthshire, Scotland
Rel: Head, Occupation: Potato Merchant
Mary ROSS, age 50, Birthplace Braes, Perthshire, Scotland
Rel: Wife, Occupation: Housewife
Mary Ann ROSS, age 18, Birthplace: Stirling, Stirlingshire, Scotland
Rel: Daughter, Occupation: Milliner
George R. LAMB, age 1, Birthplace: Perth, Perthshire, Scotland
Rel: Grand Son
James MC CULLOCH, age 39, Birthplace: Dundee, Forfar, Scotland
Rel: Servant, Occupation: Potato Salesman
Emma BROWN, age 17, Birthplace: Ireland
Rel: Servant, Occupation: General Servant
If this is the Mary Ann Ross, then it look like she's got an older sister who married a Lamb (the parents of George aged 1 above)
The 'R' - his middle name could be Ross, his mother's maiden name?
Anne