And neither of them has a nexus to the concept of "marriage" and "family"?
How many times has your application to MENSA been refused?
Let me restate: laws regarding incest have no impact on marriage, since incestuous relationships can -- and do -- take place without regard for that institution. They are neither constrained nor promoted by the presence or absence of marriage. Any "social" benefit that derives from those laws stems from the fact that preventing incest lessesn the transmission of undesirable genetic defects across generations.
Obviously laws forbidding adultery go to promote marriage. I admitted as much in my original post.
While I've never been rejected from MENSA, it's obvious you flunked your Dale Carnegie course. On the other hand, you could franchise your unique ability to be a jerk.