My 1st cousin has - and his father and his father's paternal uncle had - a congenital hand disease. They're all in the same surname line (not mine).
The disease is said to be most prominent in Northern Europeans. By paper trail, my cousin is 25% Norwegian, his father was 50% Norwegian, and his father's uncle was 100% Norwegian.
None of them had DNA testing.
Given that the congenital hand disease follows the Norwegian line, how likely is it that my cousin actually inherited more than the 25% Norwegian indicated by the paper trail?
