I'm fairly sure most (all) of us feel parent/child incest is wrong, and for fairly obvious reasons.
However, if a brother and sister are very careful about pregnancy prevention or, better, one or both of them is unable to conceive, what would be wrong with it?
BTW, I'm NOT trying to decide whether to do it with my sister (LOL). This is just a question that came to mind while in a discussion with another person.
Those studies divide into two aspects.
1) the genetic part
2) the psychosocial (taboo) part
We know that it's a taboo. No news there. And while the genetic aspect is well-known and accepted, it's still a fact that the original post was based on "suppose the couple didn't produce offspring," this eliminating the genetic factor as a consideration.
My argument is, as per a previous post, that if one pair of siblings form a relationship and it becomes seen as normal by their peers, then it is natural that others will will copy them and eventually, somewhere down the line, offspring will be produced, by accident or design, then that will be seen as normal, etc.
It is human nature and therefore, I think, should be discouraged, as it is now. As per the two articles, it is probably genetically inbuilt into most of us to not procreate with our siblings.
As an ingrained (and thus nonrational) taboo, there's little risk of it becoming commonplace or "normal."
I like this rational, non-spinned statement.