I have looked at the church records for that church in Peterborough and I am also of the opinion that the name of Charles' mother looks a lot like GIARA.However, from a phonetic point of view, I believe that it could be related to the following French surnames: girard or giroux.
However, I have not found a marriage record in Québec for a Charles Primeau (Primo) to a Girard or Giroux. They might have been married in Ontario.
I believe that Charles I was probably born about 1790 or even 1800 given that his son got married in 1845. BOy generally got married in the early twenties.So 1845 minus 44 (22x2) gives us about 1800.If born prior to 1800, Charles I would be one of the following boys baptized in the year and place shown hereunder in Québec: 1760: Chateauguay 1772: Chateauguay 1774: St-Philippe de Laprairie 1775: Chateaguay 1780: St-Philippe 1792: La Durantaye (near Québec City, not applicable) 1799: St-COnstant All but one are in the Mtl area.
The marriage record of Charles I is the key to ancestry because it would show the parents'names of Charles I.