There is no proof that these are the parents of Thomas. Assumption by Muriel Craig.

Of general interest - on the authority of M. Yann Grosset, painter,
sculptor and unihockey player, of Rennes, France - the name Grosset has
its origin in the town of Megeve - [acute on first 'e' grave on second]
in the Haut-Savoie region of France - to the west of Mont Blanc.
There is a legend, 'The Fantastic Legend of Megeve' , which tells the
tale of a prehistoric flying serpent which terrorized the Arle Valley
and forced the people to flee from the region.
A certain M. Grosset - so called because of his great size - and his
companion, M. Muffat - plucked up their courage and slew the monster.
Subsequently, Grosset and Muffat co-founded the town. It is on the
net - a beautiful ski resort:
http://www.skifrance/74173/accu-a.htm
I understand that Grossets still live there. According to Yann, some
Grossets migrated to the area south of Pisa, Italy. There is a city
there, Grosseto. Others, who had migrated to northwestern France - fled
the country - following the Revocation of the Edict of Nantes; they
went to the island of Reunion, in the Indian Ocean, to the Low
Countries, to Canada , to England, Ireland, and to Midlothian in
Scotland. Would be happy to share Yann's material with anyone who would
like to have it! Yann has done a great deal of work on the family name.