Your chance could be gardianship ( for minors) after the death of one of the parents.
It is really easy for Québec (city), wich has an index ( by name) and thé judgements ( by date). family search
For Montréal you have (on family search) the court judgements of gardianship ... by date (but, without index!).
* Did you search for an "inventaire des biens après décès" (notarial document). You can see BAnQ : "instruments de recherche en ligne", "inventaire après décès " for Montreal).
The date of the "inventaire après décès" is closed of the gardianship judgement (Superior Court).
If you never used "gardianship files" ; i suggest you, to try with the gardianship files of Québec city , take à name ( a parent died, with minor child(ren) or the names on an "inventaire" and (1) search in thé index the name of the father, to find the date. (2) with the date, search in the judgements file..
The other difficilty is thé first name of your Paquet, " Jean Baptiste" is the most common first name ...
If you can't find an "inventaire" (and the date) ask "Centre d'Archives de Montréal" if they have, near 1800, an Index of gardianship, with your jb paquet.
You can do the same thing, for his wife (with the name of her 2d spouse).
Also, censuses of 1852 and 1861 mentioned (often) the birthplace
You have, only on the census of 1891, the birthplace of the parents (that could be interesting for Dorothee). You have all the canadian censuses on bac-lac .