Hi - i wonder if ANYONE can help?!?

In the 1881 census i have a william (scott) sandliands 34 in Opie STreet Everton. he is a shop steward. with him are (the names in brackets are the middle names i've found through BMD)
* agnes 21(1860) Ireland
* william (scott) 4 (1877) liverpool; [i have found his christening record ( Name: William Scott Sandilands; Birth Date: 10 Jul 1876;Christening Date: 13 Aug 1876; Christening Place: Everton, Lancashire, England; Father's Name: William Scott Sandilands; Mother's Name: Agnes]
* jane (charmers) 3 liverpool
* agnes (mary) 1 liverpool

I think i've found William and Agnes marriage: jun 1875, William Scott Q Sandilands and Agnes Mulroney. Liverpool, st paul.

i think i've found Agnes in 1891. She has remarried Thomas Carey.
However i can't find ANY trace of this marriage either in the BMD or searching Scotlands people.
The family are lodging with the O'Neill in Wigan (40 Alelaide Street). The children are;
* agnes (mary) sandilands 10, Liverpool (possibly died mar 1880 liverpool)
* john (scott)sandliands 8, Liverpool (possibly died dec 1882 liverpool)
* catherine carey 2, liverpool
* mary eliza carey 0 wigan.

i can't trace William,his son William or Jane anywhere, nor can i find records of their deaths (BMD or Scotlands people)

I believe that Thomas is a relation of mine but i'm now intrigued with what happened to the family (it's a failing of mine when i'm trying to make connections in my tree)

I have Thomas and Agnes in 1901, in Manchester with their children and further children Frances (1896, Liverpool) and Anne (1899, Manchester) but i can't find them in 1911..

For my tree i want to find the marriage of Thomas Carey and Agnes Sandilands so i can see if Thomas is my relation However i'm really interested in what happened to this family.
Does anyone them at all?