In the late '80s, the founder of a support group for adopted children who had recently reconnected with their biological relatives coined the term “Genetic Sexual Attraction” (GSA) to describe the intense romantic and sexual feelings that she observed occurring in many of these reunions. According to an article in The Guardian, experts estimate that these taboo feelings occur in about 50 percent of cases where estranged relatives are reunited as adults[.]Emphasis added. Fifty percent is pretty substantial. It's apparently, we might say, normal.
So what's the basis for the ban? New Jersey is apparently over banning father/daughter incest. Do we have any standing, should we let go of our traditional moral standards per se, for banning it? Sure, it can lead to bad results if it happens over several generations, but in just one pairing it's of no special concern. She's obviously willing, as is he.