I would say it is immoral largely on the grounds that incest is almost certainly exploitive. Our genes are not driven to reproduce with people that are too genetically similar. When close members are having sex I would immediately infer that at least one of them is exploiting the power dynamic within the .

As a victim of brother/sister incest, ....it is simply hurtful to not know enough about yourself as a small human that you arent able to defend yourself against sexual acts forced upon you by other humans. children are sexual beings but arent ready for physical acts until they go thru puberty. With a no frills sex education and current societal norms in place, children can at least learn to determine what they should do if confronted with incest.

It is damaging to children to have to deal with sexual situations before they are grown. anyone that tells me otherwise needs to be chemically castrated. as you can tell, i feel strongly about this...my brother is not a child predator. if my parents had taught him about his body, hormones, and puberty....i would not be a victim. shame on my parents and its a shame kids are still being denied sensible sex education.

Now that the moral goal post have shifted and many jurisdictions have legalized marriage between partners of the same sex the argument of unwanted congenital defects in offspring is no longer an argument for same sex couples. Consequently the whole question has to be reevaluated. I think many people confuse morality with taste. So there is the temptation to sweep everything under the moral carpet.
I was thinking of Pitcairn. Those who know the story of the Mutiny of the Bounty might no the place. A couple of years ago the total population was estimated to be 48. The censors must just have been confused or to lazy to just count them. Now would you tell these brave souls that incest is a taboo?

Voted immoral because it leads to birth defects.

If it is done by consenting people, I have no problem, people will do what people will do, it has been done for thousands of years, and we're all still here, so ?

I am a little disappointed in the answers. They all seem to be addressing child molesting or genetic dangers. The question was phrased in a way to make it if two grown, consenting relatives want to have sex, is that immoral. Not have children, not prey on children. The hypothetical question is about sex between two consenting, related adults.

I actually don't see it as a huge deal if cousins or distant cousins decide on having some sort of relationship or even children. The genetics would be way more diverse and you wouldn't be raised in the same household so it's not the same as siblings.

Now siblings is immoral for many reasons. Your children would face repercussions of not having enough diversity in their genetics one way or another. If the siblings decided on just a sexual relationship then there is A LOT of emotional problems that could and will occur if it happened and shame since it's a very taboo thing and could ruin your relationship with them as a whole.

I can't say moral or immoral because those are social judgments based largely on social norms, but also on facts, such as inbreeding. But the truth is that pederaste was common and accepted for generations in Europe, royalty and aristocracies have in-bred publicly and even today, supposedly "moral" religious practices (not just LDS cults) marry off their children at young ages even to close relatives. I'm not sure how society has come to look down on what we call incest, but I'm sure that had a lot to do with the advent of rights-recall that even in early America, women and children were chattel and could be beaten by the male owner... until society started changing the narratives and fighting not only for women's rights, but also for the rights of children to not be abused... and our social definitions of child abuse have also changed consistently and incessantly for eternity.
As a product of a western society upbringing, I still have thoughts about incest being abuse, but, a better question is to ask the theist to justify all the incest, pederaste, and the forcing of victims to marry the rapist...Which is more "immoral?"

objectively speaking it's completely neutral. most people find it gross because they're biologically programmed to, but that doesn't mean it actually harms anyone. consenting adults can do as they please, love is love.

I cannot vote yes or no because I have to object to the use of the terms "moral" and "immoral," since both are ground in religious presumptions of a sort of natural law. To say something must be avoided BECAUSE it is wrong is, to a secular thinker, ass-backward. We are, rather, taught certain things are immoral in order to scare us away from doing things that our society or culture believes would be destructive in some way. So...the question should be "Do we think incest is harmful or not?" To me, the answer cannot be absolute, because there are exceptions, but in general I think it could be harmful, not just because of potential for genetically compromised offspring, but also because it might mess with the other social aspects of family relations, either with the specific persons committing incest or with their relations with other family members, or both. I do believe, though, like any self-respecting situational ethicist, that there are valid exceptions sometimes. Others on this thread have already pointed to some, and historically our definitions/parameters for which relatives involved would constitute incest or not. What about identical gay twin brothers who felt closer to each other than to anyone else? Personally, I think the main difficilty in that situation would be how the two handle reactions from other family members who would be upset with them.

Apart from finding it personally distasteful from an objective perspective the psychological issues and in-breeding biological problems are non nonsensical.

When playing around with sex, one may become pair bonded. As a teenager, I did with my steady girlfriend. She moved far away with her family. It was devastating for us.

Now think about the issues when one sibling pair bonds and the other does not. You are living with the tension of unrequited romantic love, with someone you will have a familial relationship with for life. This kind of mismatch will really test your patience or your relationship. So sex play with sibling without having a solid bond is hazardous, if not immoral.

On the other hand, consider a couple that falls in love and plans to delay pregnancy. Or siblings / cousins that fall in love and will have (frequent) "safe" sex. Of course, a single contraceptive is around 80% effective annually. (Always using two might be 96%. That means your odds of pregnancy are about 50% in nine years.)

If the children have 25% odds of having one (or more) active recessive diseases, the relationship is far less important than the suffering non-health of their progeny. So I conditionally call this reproduction immoral.

You don't want the tragedy of a cemented pair bond with someone who is likely to produce a diseased child.

So my advice to young people is to get your genetic testing as soon as you can afford to. Compare your test results before getting all hot and heavy. This is essential for siblings and cousins.

Because as long as it's consensual and safe, no harm is being done.

I'm pretty sure that in some cultures it's not only moral, it's standard practice. As with any inbreeding, offspring are more likely to have genetic defects than when sire and dame are from different lineage, so the only issue I CAN see would be if children result from the sex. But morality is very subjective, and often stems from religious beliefs (whether we are aware they've been beaten into us or not)...

Start out with the fact that I am assuming that we are dealing with adults and not minors. Next consider that incest is a secular taboo that religious people hold, not the other way around. In two separate instances in the bible incest would be needed to repopulate. (Adam/Eve and Noah/Wife/Sons) As for immorality:

1. There is no 100% safe sex, and any child conceived could suffer defects as a result.
2. Sex complicates things, you can lose a good friend you have had sex with, siblings are more so.
3. The Westermarck effect plays a role, sex in this setting would be prone to power differences.
4. The social taboo would be unavoidable, a long term relationship would be either built on lies or ridiculed be most people you would meet.

This does get interesting with step siblings, I know of a case where two teens were dating and then became step siblings later on. They tried to keep dating after but it failed. There are some cases where siblings have found out they were related after they had already had sex, I assume they were in need of therapy.

In the end, the morality would be highly situational, but I would say the taboo serves us well.

This question brings up an interesting realization that I had recently about theists. They determine their morality and actions based on a bunch of rules loosely (very loosely) derived from a bronze age storybook, not from an understanding of right and wrong. If Atheists don't use their rules, they don't think we can have morals, which is why they keep asking us for our set of rules. They just don't understand that morality relates to right and wrong, not to a set of rules, and they don't really have a definition of right and wrong beyond their rules.

I had fun in a xtian forum by asking theists for their definition of good and evil, and NOBODY could come up with one. Some people would say "god is good", to which I responded "and god nearly exterminated humanity, so should we measure our goodness by how many people we have killed?". They just can't conceive of actual morality.

Sex within a family system between siblings is neither moral nor immoral. It's damaging and psychologically harmful.

Morality is not a religious concept. It is derived from an evolutionary need for human survival. Incestuous relationships are counterproductive in that they do not provide healthy genetic offspring. Incest is immoral.

It goes against our evolution and instincts. Many animals avoid incest in healthy populations. That is not because of god. Humans just added social taboo.

It’s immoral because familial love lacks a sexual desire, which is probably a genetic program to prevent the deformities and abnormally caused by narrow gene pools. It’s programmed into us as gross, or damaging as mechanism to protect the species, as well as individuals. The disgust reflex is to protect us from threat to health. This person asked you this question because his/her assumption is that Atheists are immoral. Basically, ask her whether it's delicious or healthy to eat shit. Because that is the kind of question they are posing you, and it’s fucking stupid. Of course there is a phenomenon where siblings separated at a young age meet by chance later in life and fall in love and have a sexual attraction. That is understandable and I think very psychologically difficult.

Why is it immoral to a theist is the better question. If god only created one couple then he mandated incest for a time. Even without the creation myth science tells us we’re all related. Everyone in the world is no more than 15th cousins to you. It’s all relative, pun intended but sex with close relatives is discouraged by evolution more so than it is by god. I’m not sure any sex act other than Rape can be seen as universally immoral, but it’s certainly unethical and not recommended for all sorts of reasons that one would hope should be obvious with or without a god. When theists ask stupid questions like this or what prevents us from killing/raping make sure to ask them “oh so gods law is the only reason you haven’t fucked your sister/raped/killed yet? Interesting. I’ve raped and killed and fucked as many sisters as I want. And that number is 0”

The question you should have asked this theist is why do the majority of religions believe in the creation story of Adam and Eve. Christianity, Islam, and Judaism! All of these religions claim that humanity is the result of incest! Or maybe that is why the world is full of genetically stupid people.LOL

What has incest to do with a belief in God? The questioner is implying that only God (I assume either the Judaist, Christian or Muslim patriarch will do) is the arbiter of a code of morality, but morality has existed since the earliest societies, and often included the prohibition of sexual relationships between close kin.

If it is immoral when a child is a child and doesn't know any better or when they are adults. The factor lies that you can not compare a child of incest to an adult doing the same thing on consent. We set double standards as right and wrong. If you are 13 and another is 78 and you both want to break the law does it make it right for one and not the other...

I find it funny that people tend to forget the "why" of it in favor of some societal ingrained disgust.
I ponder a world where the tables are turned & its unhealthy to out breed, sex out of family would mindlessly be considered reprehensible.