Should incest between consenting adults be a crime?

[Mr.Obvious]

Are you saying that i'm neglecting The possibility that such romantic feelings are grown Naturaly, without malicious intent from, for example, one of The parents?

Close enough

Well, I'm not. 
I'm not saying it isn't possible that, for example, a brother and sister, grow up without being forced, manipulated or brainwashed into being romantically and physically attracted to one-another. And I'm not one to tell them not to fuck one another, should this be the case.
Though, due to the fact that grooming does exist and due to the fact that natural attraction to that extent within a close family setting is rather rare, it is not illogical to fear such practices to have taken place. I haven't said anything but that, so far. And I think anything else you think I said, is probably tacked on.

From this point on, however, I do want to divulge into something you brought to the table. 
The freedom to make your own choice when it comes to incest is a difficult subject. Because I agree with you fullheartedly that adults should be able to make their own choices.  As long as they don't harm others. My choice to swing my fist ends where your face begins. That sort of thing.
But I've had a fair share of clients that were cousins of one another. It's a cultural thing, one of them told me once. It's different from them, people who came here from another country, than us Belgians. (Though technically cousins are allowed to marry in Belgium. And up to less than half a century ago, such a practice was more than socially acceptable.) However, in a lot of these cases, their marriages were still pre-aranged by their family. Now one could say they still chose to go through with it. Chose to not be rejected from their family and rather do something that not only seemed acceptable but culturally normal and obvious to them. Something that was required of them. Expected.
If they really didn't want to. They could have chosen not to marry their cousin. They often married here in Belgium, a free country. We have support systems in place should someone need to flee from the wrath of their family. They CAN choose not to. So, I guess, if they choose en mass to do so, there isn't a problem, is there? There's not a point of discussion to be made?
I'm not claiming to have an answer here, Amarok. But I do want to come to a common ground that this question isn't quite solid, but rather fluid.