There are two main issues with incest: 1) offspring, which should be avoided unless you check the embryos for issues and discard any that would have health problems due to inbreeding, and 2) the possible existence of power dynamics that might make consent too questionable to be acceptable.
Two sufficiently mature (I think this excludes about 90% of the population, but that’s probably my cynicism talking) adults, who have the means to live independently (so no dangerous power dynamics), and at least one of which is naturally or artificially sterile (or who physically can’t have children for other reasons, for instance due to having incompatible genitals), sure, go ahead, have fun.
Otherwise, there’s too much risk of harming one or both of the participants, or their potential offspring.
The odds of even siblings having a child with issues are apparently pretty low still, but the issue comes from having several generations of it if it gets normalized. Like the Hapsburgs weren’t even marrying siblings, but did the cousin and second cousin marriages often enough that they ended up with a lot of inbred family members and those distinctive chins and noses.
So rather than needing to look at everyone’s family history to determine whether or not there’s been too much incest that the risk of inbred issues in the offspring is too high, it’s just generally looked down upon, which means the times it happens completely by accident (like two orphan siblings that never met or secret half-sibling affair children), it’s not as big of a deal because the odds of issues are still pretty low.
There are two main issues with incest: 1) offspring, which should be avoided unless you check the embryos for issues and discard any that would have health problems due to inbreeding, and 2) the possible existence of power dynamics that might make consent too questionable to be acceptable.
Two sufficiently mature (I think this excludes about 90% of the population, but that’s probably my cynicism talking) adults, who have the means to live independently (so no dangerous power dynamics), and at least one of which is naturally or artificially sterile (or who physically can’t have children for other reasons, for instance due to having incompatible genitals), sure, go ahead, have fun.
Otherwise, there’s too much risk of harming one or both of the participants, or their potential offspring.
The odds of even siblings having a child with issues are apparently pretty low still, but the issue comes from having several generations of it if it gets normalized. Like the Hapsburgs weren’t even marrying siblings, but did the cousin and second cousin marriages often enough that they ended up with a lot of inbred family members and those distinctive chins and noses.
So rather than needing to look at everyone’s family history to determine whether or not there’s been too much incest that the risk of inbred issues in the offspring is too high, it’s just generally looked down upon, which means the times it happens completely by accident (like two orphan siblings that never met or secret half-sibling affair children), it’s not as big of a deal because the odds of issues are still pretty low.