How about MC and Annabelle? First cousin once remove should be worst.
Annabelle is 5 degrees of consanguinity from the MC, further removed than Molly, and also only half-human, so should be legal. The MC is effectively Annabelle's father, being raised by him and Julia, so will squick some regardless.
I'm more squicked by getting with Maghda despite her clearly-shown willingness to eat people...
Tidbit: South Korea bans marriage out to 3rd cousin, 8 degrees removed, and banned marriages between people with the same surname & region of origin entirely until 1977.