OK, as best I can figure this out someone made a jump that is not documented to connect our Gilles with this Renaud/Lady Gabrielle Dubellay. If we could find this connection, however, it would bring our Sevigny line back to Louis VII, king of France, (through the Montmorency line) and to a de Sévigné chevalier (knight) from around the year 1190.
Renaud de Sévigné and his second wife, Lady Gabrielle Dubellay, did have a son Gilles born 26 Aug 1636 in Rennes, Brittany, France. I cannot find where this Gilles had Gillette De Foye as a wife. This Gilles would have been about 32 when Julien-Charles was born so his age works, and he was also from Rennes (but many Sévignés were.) As with much research in France we do not know if the record of Gilles marriage was lost long ago or still waiting for us to find it. Dulong, Jetté and others used old records from the French archives to prove that Catherine Baillon was descended from royalty, perhaps we can show Julien-Charles was also. We need to get the family association working on this project.