The earliest known ancestor is François Roy, who with his wife Xainte or Sainte Martin lived in the large town of Poitiers; both were born about 1630. They lived in the parish of Saint-Jean-Montier-neuf (attached to an abbey called Moustier-neuf in the Middle Ages; founded by William VIII of Acquitaine in the eleventh century; photo above). Their son Joseph Roy was the immigrant, coming to Québec as a soldier sometime around 1690; he was born in 1664 or 1666 and thus was about 28 or 30 when he married Marguerite, daughter of Pierre Martin and Anne Poitron (they were already in Québec, but perhaps were related to François' mother). Marguerite was the widow of Jacques Lapaille dit Charpentier. The marriage took place in the church at Québec city in August 1694. Joseph died in 1719, his wife in 1729. They seem to have lived in Repentigny. The name was common even then, and other Roy families had also come from Poitou; so Joseph was known as "Roy dit Chouigny."

Joseph and Marguerite Roy had one child that we know of: Jacques, born in February 1695 in Québec city (therefore the oldest child, but very likely not the only); he married Marguerite, daughter of Bertrand-Pierre Lalongé and Anne Ethier in February 1719, and died at Repentigny in May 1773. Their son Jacques was born around 1730 (probably also one of several children, but the family is not well documented; one brother may have been the Joseph Roy dit Chouigny who married Marie-Reine Beauchamp in 1783); he moved to St-Charles-sur-Richelieu, where he married Marguerite Marie (c1734-April 1814). Again, we know of only one child: Jean-Baptiste Roy, born January 1776, married Agathe Darcy at St-Charles-sur-Richelieu in September 1801. They were the parents of Louise Roy, who married Marcel Boucher at St-Charles-sur-Richelieu in July 1820; she was the mother of Louise (1832-1919) and of another Marcel; Louise married Maxime Martin in October 1852 and was the mother of Joseph Arthur Martin.