Bonjour Sarah,
"I just actually read online that the same researchers who found the Baptism Act for Vincent, also discovered another Vincent (dit Jeune) living with his mother (Mary)."

I have a copy of that act and it does not mention a jeune in the act. It just indicates that the marriage of Rene Brault with Charlotte Gaudier (27 jan 1674 in Coussy, France) was done in presence of Marie Renaume and Vincent Brault mother and brother of the said spouse.

No mention of a jeune (young) Vincent Brault in the act. I don't know where you found the information about a Vincent le jeune Brault but a search with GOOGLE provided nothing with Vincent le jeune Brault or with Vincent jeune Brault...

Au revoir,