It may be possible to confirm family relationships by comparing test results with Jean-Marie or other carriers of his ancestors' Y-chromosome or mitochondrial DNA.
Y-chromosome DNA test-takers in his direct paternal line on WikiTree:
Family Tree DNA Y-DNA Test 111 markers, haplogroup R-S22047, FTDNA kit #472934
Mitochondrial DNA test-takers in the direct maternal line:
Family Tree DNA mtDNA Test Full Sequence, haplogroup H5a1-T16093C, FTDNA kit #472934
It is likely that these autosomal DNA test-takers will share some percentage (beta) of DNA with Jean-Marie:
Family Tree DNA Family Finder, GEDmatch T434000[compare], FTDNA kit #472934