It may be possible to confirm family relationships by comparing test results with David 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 700 markers, haplogroup R-FGC63496, FTDNA kit #B366945, MitoYDNA ID T12483[compare]
Mitochondrial DNA test-takers in the direct maternal line:
Family Tree DNA mtDNA Test Full Sequence, haplogroup H3-T16311C, FTDNA kit #B366945, MitoYDNA ID T12479[compare]
It is likely that these autosomal DNA test-takers will share some percentage of DNA with David:
AncestryDNA, GEDmatch TQ2794914[compare], Ancestry member Davidbailey270