I checked the 1891 and 1901 census and found no Manx born Harker in either. In the births and marriages I find no marriage of a George Harker to an Elizabeth Christian or the birth of a Sissy or Hurbert, but these records are not yet complete. There is a 13 year-old George Harker living in Chirton, Northumberland in 1881, but he does not appear in 1891.
Do you have any other facts, such as ages or emigration dates?