It may be possible to confirm family relationships by comparing test results with Bill 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 67 markers, haplogroup E1b1b, FTDNA kit #B44748
Mitochondrial DNA test-takers in the direct maternal line:
Family Tree DNA mtDNA Test HVR1 and HVR2, haplogroup H, FTDNA kit #B44748
It is likely that these autosomal DNA test-takers will share DNA with Bill: