It may be possible to confirm family relationships by comparing test results with Kevin 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 RL-21, FTDNA kit #286789
Mitochondrial DNA test-takers in the direct maternal line:
Family Tree DNA mtDNA Test Full Sequence, haplogroup K1c1b, FTDNA kit #286789
It is likely that these autosomal DNA test-takers will share some percentage of DNA with Kevin: