The act of "safe sex" between siblings can be problematic because there might me power relationships between them - but if they're in a relationship as equals, and if they're both old enough to give consent, I wouldn't see it as immoral/unethical.

Game of Thrones is pure fantasy but it's rife with incest. I lean towards thinking religion swayed everyone towards believing what they chose you to believe. Aside from that apparently incest is relatively common throughout history. The deformity debate is moot because two unrelated people can create deformity as well but not necessarily with a higher degree of chance. Takeaway the religious aspect and the deformity aspect add in consensual agreement and you have two people willingly having sex. There is nothing immoral about it.

Well, sometimes safe sex is not safe, nothing is 100 percent

It is immoral if it is in the context of pedophilia and or rape. If adults choose such a thing, the risk of genetic mutation from an offspring is too high. It is selfish and highly immoral to risk bringing a defective human being into a world that is difficult enough to navigate. If related adults want children there are plenty to choose from via adoption.

An adult engaging in sex with his/her offspring is wrong, we all know the psychological effect of pedophilia and the high risk of genetic mutation.

It is immoral, because it messes up the best family dynamics. Imagine a wife or sibling think they did not get treated properly in a family setting.

I believe that if both parties are consenting and their intention isn't to have children, it is moral. Like other commenters are mentioning, incest can lead to birth defects and gentic mutations that would lower the quality of life for the offspring. If contraceptives or other methods are used, I see no reason why two relatives couldn't have a prosperous relationship.

As long as both are consenting adults then it isn't the business of anyone else. It might be distasteful, but not immoral.

Immoral if there's a kid because then he/she is screwed for life. Moral if they are consenting adults with no consequence.

Unless the couple are twins; one will be older than the other, there are issues with consent, age (being a minor), and perhaps specific circumstances could make it acceptable, but not "moral".

Taboo & Both.

It's commonly not consensual and, therefore, immoral.

It's also common that separated siblings find each other. If you don't honestly know, how could anyone claim it to be immoral.

Ironically, in the Biblical worldview, incest is not only acceptable but is the very way in which our species has survived - twice. Adam and Eve, then Noah and his happy little family. Disregard the fact that such a situation is biologically impossible. Anyway, back to the real world.

Incest itself is neither moral nor immoral. It would be immoral for children to come from such a relationship, because inbred children have a very high chance of being born with a genetic disorder. However, incest itself is no more moral nor immoral than gay, lesbian, anal, oral sex or all the other kinky categories one can find on Pornhub.

just will not have sex with my daughter

Not something that I support.

It isn't something I would do and I think it's icky but, so long as those participating don't have children, I don't care in the slightest.

First, a Christian has no way to oppose incest because it is practiced quite a bit in their religion. Second, it might not be moral or immoral. Third, in the vast majority of cases I guess it would be immoral because of the family dynamics involved. Fourth, consider the strongest case of sibling incest that might be not immoral, two people who do not know each other at all and never find out they are siblings. In that case, I don't know. Fifth, safe sex doesn't mean no pregnancies. It is difficult to not have revulsion for the idea.

Uh- do I really have to answer that? If you think about screwing your mother, father, daughter, son, brother, sister, etc. instead of the big pool of humans you have to choose from, then I'd suggest a shrink. And I don't need to hear about the flawed theory of cultural relativism. It's proven that incest, and therefore, the overlapping of genes, causes serious physical and mental problems.

non sequitur , the question is too vague to be answered definitively one way or the other. An incestuous relationship between legally consenting parties is none of my business provided that intercourse does not result in the birth of a child. There is no sensible reason to subject a child to that kind of genetic predisposition to defect and social scorn. Otherwise, I couldn't give a toss.

first of all, I know people who are the products of incestuous rape that have no deformities. I also knew a lot of people who come from parents not genetically related who have major disabilities, so that isn't an issue. Besides, off you're having safe sex.....

This is one area where we are taught that is gross. But since it happens, it's perfectly natural.

The fact is that morality isn't about what you think other consenting adults are doing. Morality is about conducting yourself with integrity, and not allowing your preferences to hurry other people. So incestuous rape is immoral. Incest between consenting adults is not. Just like any rape is immoral, but sex between consenting adults is not.

I don't know if I would say that it was moral as much as i don't think its inherently immoral. Of course that statement has to be qualified. I think if both parties are consenting adults, and that assumes that there is no coercion, then I can see anything objectively wrong with it.

I am saying immoral just based on criminal statutes. There are also issues of genetic disorders from incest.

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?"

Because no age parameters or relationships were given, I am going with immoral under the assumption that there is a significant age gap, disparate levels of education/power/wealth, or other inequalities that would put one party at a disadvantage. For example, a girl and her Father vs two 35 year old first cousins are vastly different scenarios.

The offspring will be freaky mutant kids.

Well...if you are looking at it from the biological perspective of reproduction, there is that risk of passing on genetically inherited flaws and afflictions (weak chins, poor vision, disabilities) so it may not be wise. On the other hand, if you don't have any genetic markers for health concerns you would strengthen your bloodline and could lead to a better, faster, stronger (depending on strengths) specimen. Kinda hard to get past the 'eww ick' factor. When you are your own aunt, things get weird. But you probably will get something better than socks and an autoharp cd for your birthday. I don't think that immoral or moral are really the best choices because morality generally is passed down through religious dogma. Better to say gross or not gross. Not easy to get out of the gross camp. If it were a social norm with which I had grown up I would likely feel differently.