Like you said the name of Adèle Brien is on the census of 1871-1881-1891.
You also mentionned that the record for the marriage of Pierre Messier & Adèle Brien (1880-Wolfe) is not the one.
I was wondering if you saw that Church record, because at the end the priest wrote down the name of Odile, Pierre, Ursule, Philippe, Espérance and Constance, the name of sponsors for each child and a note to invite the couple to accept those children who were living with them before the marriage.
My understanding is that the children were baptized that same day (I did'nt find any birth records).
So It would explain why we see the names of the children on the census before the marriage.

What do you think?
I have more info for this family.