Now, if every party is an adult and capable of informed consent, it is possible to test for likelihood of genetic defects based upon the parents’ genes. So, I can’t think of a non-subjective objection if, for example, they met for the first time as adults and didn’t know of such relation. Still pretty weird to me but I don’t think it’s anyone’s place to interfere with healthy, loving relationships.
I was actually thinking more about this when I replied to another comment yesterday. I’d be willing to bet that this happens at the very least more than people think, and I’d be willing to bet there are at least some couples out there who simply do not and may never know they’re genetically related. Think about one deadbeat dad, for example, in a given area. Multiple children from multiple mothers. Do you think anybody in those families have any idea of exactly how many cousins, for example, they have living in the area? Worse, if the father is unknown or out of the picture or whatever, there’s the possibility of people out there who may be sleeping with their half-siblings and not even know it. I’m not saying there are entire towns of people out there who should be singing Sweet Home Alabama or anything, but I’d be willing to bet the number is above zero.
In cases where children could be produced, I’d fully support incest being illegal. You are subjecting potential children to the increased risks that come along with being a product of incest, along with putting a social stigma on them that they will never be able to shake. I do not believe a child should literally have to spend their lives literally paying for the sins of their parents. But if there is no possibility of children being produced (Say, for example, a homosexual couple or if the woman is beyond child-bearing age) and there’s no power dynamic influencing one or both of them (For example, a couple who have been together for a while and didn’t know they were related), I can’t really say I’m against it either. I don’t have to agree with their decisions, but if they’re not hurting anybody else, I don’t believe it’s my place to say no to it either.
(And I’ll say again, I’m talking about healthy, consentual relations between two adults who happen to be related. This should not be interpreted to be justification for some 60 year old guy to try to marry his 13 year old niece, or cases where one sibling (or parent or cousin or whatever) pressures another into entering a sexual relationship they wouldn’t have otherwise consented to. Those cases are just straight up rape, and should be treated as such – with the creep thrown in jail to rot for the rest of their lives.)