Marie D’Aoust (Guillaume's sister) married Azor Frussart, a tanner and shoemaker from Sissonne. Six of their children were baptised in Sissonne:
a) Hubert - July 2, 1668. He later went to live in Paris.
b) Louise – November 11, 1671.
c) Marie – December 27, 1673.
d) Nicolas – December 23, 1676.
e) Anthoine – October 5, 1679.
f) Anne – June 26, 1682.
He was in consequence, Guillaume's brother-in-law.