It may be possible to confirm family relationships by comparing test results with Peter 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 500 markers, haplogroup R-BY3164, FTDNA kit #127469
Mitochondrial DNA test-takers in the direct maternal line:
Family Tree DNA mtDNA Test Full Sequence, haplogroup U2e1a1c, FTDNA kit #127469