Following on from Jean's thoughts, on the 1891 census there is a John Clague aged 19, with Thomas Cain 50, Margaret Cain 49, Margaret Cain 25, and Clara Cain 18, this is from Brian Lawsons Census Index , ref 4688.4.1.
Then found the same family on IGI , 1871 census at 64 Duke Street , Douglas with Servants/Employees, but no John Clague or Cain.
From 1881-94 , Brown's directories etc show Thomas Cain as a butcher..
Can someone check the 1891 census to see John Clague's relationship with Thomas, may just be Servant.
Cheers
David Dwyer