I have found the following entries on LDS. Some of these may well be your family.
Is it possible John married Mary Crowley?
Marian
1. MARY COTTER
Christening: 13 MAR 1873 Roman Catholic, Inchigeelagh Parish, Cork, Ireland
Parents:
Father: JN. COTTER
Mother: ELLEN COLEMAN
2. MARY COTTER
Christening: 03 APR 1842 Roman Catholic, Inchigeelagh Parish, Cork, Ireland
Parents:
Father: JOHN COTTER
Mother: MARY CROWLY
3. Mary A. Cotter
Birth: 1842 , , Ireland
Death: 1900
Parents:
Father: John Cotter
Mother: Mary Crowley
4. MARY FOLEY
Christening: 02 MAY 1818 Roman Catholic, Inchigeelagh Parish, Cork, Ireland
Parents:
Father: ANDREW FOLEY Family
Mother: MARY LEARY
5. MARY CROWLEY
Marriages:
Spouse: JOHN COTTER Family
Marriage: 02 JUL 1837 Roman Catholic, Inchigeelagh Parish, Cork, Ireland
6. MARY COTTER
Christening: 03 APR 1842 Roman Catholic, Inchigeelagh Parish, Cork, Ireland
Parents:
Father: JOHN COTTER Family
Mother: MARY CROWLY
7. 1881 Census of Canada
Household:
Name Marital Status Gender Ethnic Origin Age Birthplace Occupation Religion
John COTTER M Male Irish 40 Q <Quebec> Machinist Catholic
Ainastia COTTER M Female Irish 39 Ireland Catholic
Edward COTTER Male Irish 9 Q <Quebec> Catholic
James COTTER Male Irish 6 Q <Quebec> Catholic
Henry COTTER Male Irish 4 Q <Quebec> Catholic
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Source Information:
Census Place East Ward, Sherbrooke, Sherbrooke, Quebec
Family History Library Film 1375835
NA Film Number C-13199
District 55
Sub-district C
Page Number 23