That same family in the 1891 census:
Montcalm, Provencher, Manitoba
Francois Mercier, age 64, born Quebec, farmer
Philomine, age 52, born Quebec
Joseph, age 17, born U.S.
Rosalie, age 15, born U.S.
Elisabeth, age 13, born U.S.
Arsina, age 12, born Manitoba
Hector, age 6, born Manitoba
Manitoba Vital Statistics have an online index:
http://vitalstats.gov.mb.ca/Query.php I don’t see Arsina’s birth listed but her brother Hector is there. He was born Joseph Hector Henri Mercier, 7 Aug 1884, RM of Montcalm, and his mother’s name is shown as Philomene GENSON.
The marriages of some of the Mercier girls are listed too. Any of them can be ordered for $12.00 each and should give a more specific place of birth and their mother’s maiden name.