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:
AncestryDNA Paternal Lineage (discontinued), haplogroup R1b
Mitochondrial DNA test-takers in the direct maternal line:
AncestryDNA Maternal Lineage (discontinued), haplogroup J +
Family Tree DNA mtDNA Test HVR1 and HVR2, haplogroup J
It is likely that these autosomal DNA test-takers will share some percentage of DNA with David: