>>149750488
if they're not related there's literally nothing wrong with it whatsoever. Namor is atlantean royalty, royal families adopting people into it and then having them marry in as well to simultaneously legitimize their claim and keep power within the royal family is EXTREMELY common across history. Lu Bu was such a capable general he was adopted TWICE by two different dynasties in the Romance of Three Kingdoms period.
"she's my cousin except not related since her family was adopted in" is literally prime marriage material for any royal, it's like you guys don't even play Crusader Kings....