John,
Jack’s grandfather, Edmond 1889-1956, had five siblings-James 1880-1950, Alma 1883-1908, Alphonse 1886-1970, Laura 1892-??, Alfred 1898-1952.
James had a son, Sylvio 1908-1996, Sylvio had a son Paul 1939-1948.
There are four generations of Nicolas Gamache. The first was born in 1601, died in France in 1680. He had a son Nicolas, born 1639, died 1699 in Canada, and He had a son Nicolas born 1680, died 1734 in Canada. He had a son Nicolas, born 1707, died in South Africa. No record of the year he died.
Alphonse had a son, Elmo J.1916-1980, and a daughter, Lucienne, 1911-1972. She is Lucienne Gamache, and she married Leo T. Moore. Saying that she may not be the Lucienne, you’re looking for but is the only one I can find.
Alfred had a son, Romeo B. 1926-2009
Sylvio, Elmo, Lucienne (if she’s the right one), and Romeo were all 1st cousins of Jack’s dad. Paul is a 1st cousin once removed.
I hope this helps you in your search for who they are.
Beth