Just a reminder, Before I added the "no" option there are only "my sister is sexy dear" and "she always want me to cum in pussy" option. Pretty pathetic for a poll seeing both of the former option means practically the same thing.
Looking at the text just below the title, I would say incest is not the main concern over here.
Having sex with someone married to another person is something frowned upon. And in my opinion, It would be a bigger concern than incest.
I would say -- Incest is a non-issue, But everything else related to the act matters. Whether or not both the parties are on the same page of understanding and who else they are creating a problem for in the act.
I didn't touch the aspect of inbreeding depression, As creating babies knowing that they will have genetic defects down the line is just carelessness. [Please don't think of "carelessness" as a mild word. ]
In case there are rules for commenting here, I didn't find them (checked FAQ).
I was here "late in life", And both parents were their family's baby. So, I only know OLD as family (96% of 'em are dead, Now). And 2nd cousins don't count. You don't even need a blood test to marry one.