Hi All

With Sancti's possible death entry for mother Mary, there is this possible census entry in Scotland for 1901. The transcript is messy and I think a couple of households may have been jumbled together, but I think this might be the core entry for the Coulters:
Sam Coulter 29, car driver b. co Armagh, Ireland
Sarah Coulter 4 b. Glasgow
Wm J Coulter 2 b. Glasgow
Sarah J Coulter 27, sister b. co Armagh, Ireland
Address: 25 Dunn St, Bridgeton Glasgow (fits well with the location that Sancti found)
Canadian, if you have the birth cert for William John, this should include the date and place of parents' marriage for reference when searching on SP, although from the info by Carole, there looks to be likely one possible entry.
Monica