well, first off, the boy born on 12 January 1768 is baptized Joseph; Joseph is buried in 1773.
Jean Baptiste is baptized on 23 June 1782 in Châteauguay https://www.genealogiequebec.com/Membership/LAFRANCE/acte/643940
IGD - Drouin collection (membership)
there is another Jean Baptiste baptized 18 Feb 1786, again in Châteauguay https://www.genealogiequebec.com/Membership/LAFRANCE/acte/644180
Jean Baptiste Jeandron (sic) married Catherine Henns (sic) on 4 September 1809 in Châteauguay, listed as of age on the record. https://www.genealogiequebec.com/Membership/LAFRANCE/acte/2353443
Jean Baptiste Jeandron (sic) married Catherine Jeandron on 26 Aug 1811 in Châteauguay, consanguinity noted he is of age on the record https://www.genealogiequebec.com/Membership/LAFRANCE/acte/2353560
This is not the same man, 2 brothers with same name, there are children born to both couples concurrently. And it happens fairly often that 2 siblings have the same name, often given by the godparent of same gender.
Catherine Hins, wife of ''Charles'' Gendron, died 2 Feb 1837 buried 4th in St-Clément de Beauharnois, age 50 per the record. https://www.genealogiequebec.com/Membership/LAFRANCE/acte/4257979
''Charles'' Gendron, widower of Catherine Ens (sic) remarried on 8 May 1838 in Vaudreuil with Victoire Léger, widow of Jean Marie Chales (there are children) https://www.genealogiequebec.com/Membership/LAFRANCE/acte/3475810
Victoire Léger, wife of Charles Gendron, died 17 Aug 1847, buried 19th in St-Clément de Beauharnois, aged 48 https://www.genealogiequebec.com/Membership/LAFRANCE/acte/4258822
His last known child who marries is Philomène Gendron (2nd marriage), to Paul Montpetit in St-Clément de Beauharnois on 29 Jan 1861, and Charles is cited present at the wedding as father of the bride
Obviously he took his father's given name, probably to reduce the confusion with his brother, happens a fair bit.. I also cannot find a funeral for him in Beauharnois on the stated date, also checked St-Timothée, no go either. Can't find a funeral for his brother to see if there was a way to determine which brother married who. Presume the eldest married first.