
In my country, from a legal point of view, yes, even if you're not related by blood ^^
That means you can't marry but other than that nothing happens: law can't decide who you love (except of course for special relationships like with underage partners or whatever). I don't know what would happen if a baby was born from an incestuous relationship though.
Btw, cousins aren't considered incest ^^ (even if it's still not safe for the child -if there's one- on a genetical pov)

That's a good question... I have no idea ^^' my knowledge in that part of law isn't really good XD
But I don't think in that order would be a problem. In the end it's the instance delivering the marriage certificate that will decide.
I think the reason is that step-siblings are considered siblings, while the parents are completely unrelated and were not raised together. In the end it all comes back to "close family relationships should not evolve in romantic love ones", because of society taboos ^^

no. in no western region would that be considered incest . not by law. only point is if u want to marry u have to proof the no blood relation ( birth certification diff parents) . and law only afirm for that if , and only if! , the "step" parentpart adopted the not blood related child.
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