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As long as it doesn't lead to kids being born, and all parties are adults, can't really have much issue with it.
And the whole issue about inbred kids being a problem is also blown out of proportion, it's only bad if your family has a repeated history of it over generations. If your family hasn't though, you could have a whole brood of kids with even your closest relative and it's statistically no more risky than a stranger. It's just bad when yeah, like the muzzies for example, every generation or every other generation, it's cousin marriages consistently for your entire family history pretty much.
Though that's just an observation, again my original point is to not split hairs and just put a foot down saying no to any kids being born from it. Just easier to make that your ground rule.