Ok so heartless and nobodies didnt exist in BBS right? only unbirths.
IF heartless are a heart and nobodies are the body and soul, then the unbirths are the whole thing(body,soul and heart) but they are kinda asleep.So here goes my little theory, unbirths are the whole thing as i said earlier, they are made of darkness of course, but as we know when the darkness invades a heart a heartless & a nobody are created.So why if the unbirths are made of darkness they havent turn into a heartless/nobody? Cuz they are kinda like sleeping though they are awake, the process of making a heartless/nobody cant start cuz of that.So thats why they are called unbirths, they ARE there full of darkness but the ones that are supposed to be born(heartless nobodies)havent, so the whole UNBIRTHS term is referring to them.
EDIT:now you can bash this
IF heartless are a heart and nobodies are the body and soul, then the unbirths are the whole thing(body,soul and heart) but they are kinda asleep.So here goes my little theory, unbirths are the whole thing as i said earlier, they are made of darkness of course, but as we know when the darkness invades a heart a heartless & a nobody are created.So why if the unbirths are made of darkness they havent turn into a heartless/nobody? Cuz they are kinda like sleeping though they are awake, the process of making a heartless/nobody cant start cuz of that.So thats why they are called unbirths, they ARE there full of darkness but the ones that are supposed to be born(heartless nobodies)havent, so the whole UNBIRTHS term is referring to them.
EDIT:now you can bash this