Hi.The short answer is Yes.Here is the family in 1891:
1891 Census of Canada about Ozeline Groulx Name: Ozeline Groulx Gender: Female Marital Status: Single Age: 15 Birth Year: abt 1876 Birthplace: Ontario Relation to Head of House: Fille (Daughter) Religion: Roman Catholic French Canadian: Yes Father's Birth Place: Quebec Mother's Birth Place: Quebec Province: Ontario District Number: 111 District: Prescott Subdistrict: Alfred Household Members: Name Age Alexis Groulx 44b. 1847 Que. Philomere Groulx 39b. 1852 Que. Louise Groulx19b. 1872 Ont. Leger Groulx 17b. 1874 Ont. Ozeline Groulx 15b. 1876 Ont. Ludger Groulx 13b. 1878 Ont. Albina Groulx 11b. 1880 Ont. Joseph Groulx 7b. 1884 Ont. Sara Groulx 5b. 1886 Ont. Octavio Groulx 3b. 1888 Ont.
Here they are in 1881:
1881 Census of Canada about Alexis Groulx Name: Alexis Groulx Gender: Male Marital Status: Married Age: 34 Birth Year: 1847 Birthplace: Quebec Religion: Catholic Nationality: French Occupation: Farmer Province: Ontario District Number: 103 District: Prescott Sub-District Number: G Subdistrict: Alfred Division: 2 Household Members: Name Age Alexis Groulx 34 Philomen Groulx 29 Celima Groulx 12 Louise Groulx 9 Leger Groulx 7 Ozeline Groulx 5 Eugere Groulx 3 Malvina Groulx 1
I don't see a Philomene or an Emma for a child, but perhaps Celima, b. 1869 is yours.
This family is living next door to a St. Jean family, Xavier St. Jean, b. 1838 Que. & his wife Justine, b. 1839 Que.
This is very likely their marriage:
Francois Xavier Martin dit St. Jean (Joseph & Magdeleine Watier) m. 3 Jun 1861 Vaudreuil (St-Michel), Quebec Justine Leduc (Amable & Sophie Therien)
So, I think it's safe to say that St. Jean IS a dit name for Martin, especially in your family, and as dit names they were used interchangeably.So, your Philomene could have used one or the either or both names.