On his death Registration his mother was Elizabeth (domestic servant), no father listed.
And, on his marriage registration to Clementina he states he is a widower, the son of Thomas Sunter (joiner, journeyman) deceased and Elizabeth Sunter, ms Sunter.
His age at the time of marriage suggests he was born in 1848. In the 1891 Census he claims he was born in Glasgow. A search within Glasgow yields nothing a search within Scotland 1845-1850 yields one. Thomas to William Sunter and Elizabeth Pebbles in 1848 (Kilconquhar, Fife). I found nothing more on this Thomas. However, there are holes in the OPR's there could be others unrecorded.
However, in the 1851 Census, there is only one Thomas that fits the age, he is 3, the Grandson of William Sunter a Weaver living in Kilconquhar, Fife along with his wife Elizabeth and their family. This Thomas is identified as being born in Glasgow. There is also a son Thomas but he is only 14 so it can't be the father...well I hope not. I looked for a daughter named Elizabeth but found none, there is a daughter named Hellen age 21 living with the family and listed as being unmarried, but the rest would be too young.
In 1861 Thomas is 12, still with the family, same Parish, same place of birth and but elevated to a son (not uncommon).
1871 - he doesn't appear to be in Scotland.
There is no Elizabeth Sunter in the 1851 Census that fits the description that I found in fact there is only 4 in all of Scotland who could be the mother albeit on the far side of 40.
Thomas' first wife Elizabeth Paterson died in Brechin in 1883.
In the the 1891 Census children were:
Thomas b England (age 17)
Alexander b Brechin
William b England
Jessie b Boness
Since he married Clementina in 1884 these are her children with the possible exception of Elizabeth.
Elizabeth
Andrew
May
Isabella
Robert 2 mo circa 1890/91
There could have been more children born after 1891.
It is possible Thomas married Paterson in England as there is no marriage in Scotland and that the first child was born there. If found, it may hold more clues as to his origin.
Don