this is totally Korean but if we're going by Japanese laws cousins can marry ⁄(⁄ ⁄·⁄ω⁄·⁄ ⁄)⁄
why worry about such things if right now their "feeling"? are all about getting free chicken and not having their porn videos erased (●￣(ｴ)￣●)
people have different concept about "blood related". you may say that cousins couldnt marry. however, other people, use term 'sibling' as kids who have same blood from father, mother, or both. outside of this circle, those kids can marry eventhough they have "blood related" from grandpa/ma.
In a number of western countries, cousins can marry so long as they aren't first cousins~ Personally, don't get it; but, you've got to wonder what sort of situations have cropped up that the law says that it's a thing XD
so she said they aren't blood related siblings, but they are cousins, so they do have the same family blood ties. And since he's her adoptive brother, I think technically from a legal case they are blood-related (step) siblings and can't get married; just throwing that out there