Forgive me, Michele, I cannot remember if I already answered your posting.
The website that lists the Jewish Guyons is:
JewishGen.com
The
Guyon line suddenly appears around 1500. That is a time when many Merranos (Jewish families hiding their faith/identity by outwardly joining the Catholic church)flooded into France, mostly from Spain and Portugal. It is merely a possibility but '
Guyon is close to the Hebrew family name 'Dayan' which means '
Judge. 'Dayan' was changed to'Dion' by Jewish families who fled to Russia centuries ago. This family line still exhists today (descendants of the tribe of Dan).