Check the witnesses

Something drew me back to a branch of my DAWE family that emigrated to Quebec.
I'd not found anything conclusive about them after the 1881 census of Montreal.
This time round the Drouin collection showed an Emma Elizabeth DAWE marrying an Alexander COWAN in Montreal in 1890. unlike several marriage entries her parents weren't listed, and as I didn't have an Elizabeth in her name, the identification was tentative.
Witnesses: J A & Katie SMART.
That sounded familiar.
Back in 1881 a lodger in the household was one Julius SMART.
Took a few short searches of the Drouin collection to turn up a marriage of Emma's sister, Catherine Thomasine Mary DAWE, shown as daughter of Nathaniel DAWE & Catherine nee WATTS, witnesses Nathaniel DAWE, and Isaac Nathaniel DAWE (Catherine's father and brother).
So at least father, sister, and one brother Nathaniel had all survived beyond 1881.
Subsequently Catherine and Julius SMART & family, have been found up to 1911, parents Nathaniel and Catherine, with son Isaac were found in 1891, indexed on ancestry as DANE, then parents in 1901, but not a sign yet to be found of Alexander and Emma Elizabeth COWAN after their 1890 marriage - anyone know what happened to them?