Maybe I'm the only one who is confused, so here is a timeline of "known" records. I have photocopies or printouts of some stuff, but I don't know where it was all originally sourced. It is not always clear which Pierre is which, so I have listed them below as it was recorded, to be sorted out below.
1727 - Pierre Cuvillier born of Francois and Catherine St. Paul
1745 census - Pierre Ducoste "Coureur", aged 66 (= born c.1679)
Catherine St. Paul, aged 45 (= born c.1700) a widow, living with son Baltazard, aged 15
Marie Magdaleine Kable aged 36 (= born c.1709) wife of Jacques Cure
MMK & Jacques have 2 sons & 2 daughters, all under 12 (= born 1733-1745)
1747 - Antoinette, wife of Pierre "Coureur" buried
1749 - Pierre "Coureur" marries MM Kable (a widow)
1749 - Pierre "Coureur, SON OF PIERRE AND ANTOINETTE" marries Magdaleine Kable. [emphasis mine, 2 records]
1752 - Pierre Ducoder, son of CSP, marries Marie Layeux.
1752 - Pierre Cuvillier marries Marie Assayer
1753 - Pierre II born of Pierre and Magdaleine Kable
1754 - CSP buried
1758 - Pierre & Magdaleine give away his stepdaughter
1766 census - Pierre aged 75 (= born c.1691)
a wife aged 50 (= born c.1716)
Son aged 11 (= born c.1755)
1773 - Pierre II marries Henriette Rabalais
1785 census - Pierre, aged 32 (born c.1753)
1) Pierre Ducoder is actually Pierre Cuvillier, who married Marie Mayeux (who is actually Marie Assayer) in 1752. This is an easy conclusion, unless you believe
a) that Ducoder is a variation of Ducote, and
b) that Pierre I married a third time (to CSP, the record of which is lost) but then later had a child (Pierre II) with his second wife?
[Sidebar: My 1980 edition of Gremillion's "Some Early Families..." notes the marriage of Ducoder to Mayeux, but does not claim Ducoder is a variant of Ducote as I previously thought. The 1982 edition of Gremillion's "Commentaries" does not mention the Ducoder-Mayeux marriage. Either the mistake was realized or Ducoder is a unique family name that begun and ended with that particular Pierre.]
2) On the basis of the previous conclusion, as well as the fact that she would have been about 53 when he was born, Catherine St. Paul is not the mother of Pierre II. She was born after Pierre I, so she can't be his mother either. As Catherine was not known to remarry after Francois' death, the parents of Pierre Ducoste/Ducote I are therefore unknown.
3) The marriage records showing Pierre as the son of Pierre and Antoinette are contrary to everything else. There are no known records of a child between Pierre I and Antoinette, nor does the census record any other possible Pierre Ducote around this time or age. "fils" must be a typo.
4) The census records are as confusing as the names and not to be trusted entirely. According to the 1745 census, Pierre Ducoste is listed as 66 years old, which would have made him 87 years old in the 1766 census. [That is, unless Pierre Ducoste is not Pierre Ducote I.] Magdaleine Kable Ducote was 36 years old in the 1745 census and therefore should have been 57 years old (not 50) in 1766. Pierre II is known to have been born & baptized in 1753, not 1755 as the 1766 census implies by his recorded age.
By the 1745 data, Pierre was 74 when Pierre II was born in 1753 and Magdaleine would have been 42. If you believe the 1766 census, however, Pierre I was 62 and Magdaleine was 37 when Pierre II was born. This is more likely. Fortunately, the 1785 census agrees with the birth & baptismal records for Pierre II, but it would have been nice to have another data point for his parents.