I think the real issue about incest is how easy it is to result in power imbalance and therefore abuse. It can happen in relationships between siblings, since you've been raised together and your entire network of family relations is connected to your sibling as well. Think things like "if you don't do this I'll tell everyone about us" and harming your relations with family members after a breakup.
I'm not even going to go into parent/child relations because that's pedophilia and rape, and nobody should even try to defend this.
There is the matter of a slightly increased risk of genetic diseases in children of these couples, because the chance that you both carry the same rare recessive gene is higher than for random strangers. It's not a "very high risk" or anything, just higher than average. So genetic counseling for these couples is strongly advised.
In this particular story, however, there is neither a power imbalance nor risk of genetic diseases, so any complaints people have about this couple fall into the category of morality, as in, what people consider inherently right or wrong.
In the issue of power imbalance, a relationship like this one would probably be much healthier than a pseudo-incest relationship between stepsisters who were raised together.
last edited at May 10, 2020 10:33AM