Bridget's border crossing record indicates her mother is living in Castlemartin, County Meath, so that is likely where Bridget was from, but not necessarily Ernest.
1921 Canadian Census Glacier Post Office, Kootenay West, British Columbia
Croft, Earnest, Head, aged 36, born England, parents b. same, immigrated 1906, signal maintainer, railway tunnel Croft, Bridget, Wife, aged 36, born Ireland, parents b. same, immigrated 1911 Croft, John R., Son, aged 7, born Saskatchewan Croft, Anna M., Daughter, aged 5, born Saskatchewan Croft, Elizabeth, Daughter, aged 1, born B.C.
1906 Canadian Census MacDonald, Manitoba
Croft, Ernest, aged 16, born England, servant, immigrated 1905 I wonder if Ernest came as a British Home Child to Canada as I find an Ernest arriving in 1904 with a group of Dr. Barnardo's Children.