A very difficult question - my instinct says immoral but my brain says moral. I think it would have been interesting to ask the theist his opinion on Lot and his daughters though!

Consensual. A child is not accountable and cannot consent. Sexual relations between children is quite common, even siblings. Not being accountable implies innocence.

If the adults are siblings, why is it gross other than the genes issues? We are coming to an age that we can have the aging gene removed and some will want to have children. If that is happening, so are other breakthroughs that can manipulate the genes.

Sex is sex. It's why we're here -- to find happiness. Most people do it through sex.

The whole question revolves around any harm being done. If the two people are adult and it is fully consensual and there are no health consequences then two people are having enjoyment and no harm is done to others. It is immoral to deny two people enjoyment if there is no harm to any other person.

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 take the position of Lazarus Long

Sin lies only in hurting other people unnecessarily. All other sins are invented nonsense. (Hurting yourself is not sinful--just stupid.)

There does appear to be an instinctive aversion to "incest". An individual is unlikely (although this research is decades old) to be sexually attracted to someone with whom they were raised. This obviously has exceptions and does not preclude the exploration small children perform or incest between blood relatives who've not been raised together (there've been a couple of very sad cases of this in the last decade.) The morality of it is dependant on your society, and often your status within that society. Are you a Hapsburg?

I posted immoral, so I could comment. I think it is moral for consenting adults who do not have children. Immoral when it includes pedophilia, or among minor siblings because their ability to reason is not established.
There was a cousin, I fell in love with, late in my life and had it not been for the fact that geography and life circumstances made it impossible, I might have even married him. We would have made an awesome couple. I refused to have sex with him because it would have been far to difficult to end when we would have to be separated for a year at a time.

OK, if we define it as between 2 consenting adults, and there is not the issue of in-breeding, I still have the eeeewie sensation. gross. Consider Albert Einstein and his 2nd wife, they were 1st cousins as their mothers were sisters, they were also 2nd cousins as their fathers were cousins. Cleopatra was the product of sibling incest that went back generations. So this question boils down to the definition of morality. I am against incest by gut feeling, yet the majority of my family and friends consider me immoral because I am divorced others because I am sometimes in multiple relationships. I am honest and open about it and deceive no-one and never cheat when in a committed one on one relationship, so that is ok to my own sense of morality, incest would not be. But am I right to judge another? Is it any of my business as long as their is no victim?

The taboo against incest is confused by the religious element. The taboo serves a purpose. It is to insure that children will not be victimized, to have a childhood among family, without this threat. Obviously there is some threat to serial incest through birth defects( Google' Hapsburg chin', but its main purpose was to protect children from family members.if two adult relatives decided that they wanted to have sex, I would say that is their business.

I voted moral with the mindframe that it's being done by consenting adults who are mentally and psychologically sound. If the consent is there, I don't care what other people do. Not necessarily moral or immoral either way. As long as they don't pro-create of course.

To each their own really but I personally find it gross because it was bad enough having to hold my sister's hand after a quarrel, let alone touching each others nasties or cousin's for that matter..

Safe sex is safe most of the time.

Not having a sister, and all of my cousins being happily married, it's not a realistic issue for me.

Just look at some of the royal families. It seems to me like a broad gene pool's advantages outclass breaking the taboos on family relations.

Life is a sexually transmitted disease that is inevitably fatal.

well the biggest concern is health . is it safe ? if pregnancy occurs what are the odds the child has some sort of defect ? you have to think of the child being born as well the torment hes going to endure when his peers find out . as times change maybe itll be more accepted and safer. as of now its not safe ( someone pls correct me if wrong ) and it issnt accepted ( think about what his peers will think ) . as of right now i can't agree with it exspecially the health hazzards

Biologically stupid, and the quickest way to ensure future generations are subject to bad mutations.

Are you nuts?

I would ask him, "Was it moral or immoral when Josh Duggar... Christian... molested his sisters and Mike Huckabee... former pastor... defended him?" There was no penetration... that's about as safe as it gets.

I said immoral and it has nothing to do with religion. On the rare case that 2 adults not raised together meet and have sex, then find out they are siblings, either half or full, it's just some shitty luck. If they want to continue that relationship, then by all means knock yourself out. If they are raised together as brother and sister, then that's just gross and you need your head examined. Having sexual feelings for a sibling should not happen. It's part of being human to contain different and deeper emotions towards parents, grandparents, siblings and our own children. We love them, protect them and respect them. Animals in nature do not have this. No sexual feelings should come into play unless you are mentally unstable.

If you were in an adult consensual sexual relationship with your sibling, would you be able to tell your best friend? Your parents? Talk about it with the girls over cocktails? Laugh about the queef you let loose after getting pounded all night by your BROTHER?! Man, I don't know about morals but I do know if you hide or lie about things, it's usually because you know it's not right.
I don't have brothers but have thought "if I had a brother and he was a hottie, would I ever find myself sexualizing him?" I can be a bit of a floozy! But I'm pretty sure I wouldn't be able to introduce him as my new boyfriend at the office party. "Oh, tell us all how you met!"
"Mom brought him home from the hospital when I was 2."

There are two types of incest, consensual and forced. Forced could also mean that the more vulnerable participant was manipulated verbally and/or emotionally. Consensual incest implies that both parties are fully aware of the consequences of having a child with genetic aberrations is increased. As long as each party feels mutually respected and has the option to stop at any time, their incest is none of my business.

Perhaps mine is not going to be a popular opinion, but my moral compass is governed by the principle of doing no harm. If incest is consensual and they aren’t trying to reproduce, then it does not harm anyone and both consenting adults have a right to be happy.

You should ask said theist how Adam and Eve populated the earth. Or remind them of the daughters of Lot.

it is moral because it is between two consenting adults. otherwise you could ask the same question in the context of same-gender sex. it all depends on the dogma and societal do's and don'ts of your culture... some say it's immoral for two men or women to have sex. awkward, but not inherently right or wrong IMO...

Two non-religious issues with incest, as I see it:

1. The potential for genetic problems in any offspring produced.
2. The possibility of parents or older siblings grooming children for sexual activity. Consider a father raising his daughter to be his sexual partner the day she's legally old enough to consent, and this being perfectly acceptable in law.

The former, I will leave to science. The latter is a violation of the kind of trust that a child should be able to place in close family.

I find it rather tragic when two people meet, become romantically involved, and then discover that they're related closely enough to make their relationship incestuous. There has been no grooming at that point. Just a twist of fate that made their relationship unacceptable.

What's particularly interesting is where the boundaries lie. In the UK, for example, sex with a first cousin is perfectly legal. Elsewhere in the world, it's considered incestuous, and carries the same legal consequences and moral outrage as a parent and child or a pair of siblings.

I voted immoral because of the genetic concerns in future generations. I qualify this however by saying that safe sex practices and a "healthy psychological relationship" (if that's possible) would have to be used. This is something that I feel isn't practiced in most incestual relationships therefore incest in the practical sense is immoral.

I have to say my brother sister and I were abused sexually by our much older uncle; so knowing that that is the most common occurrence of incest it is IMMORAL.

Having said that our DNA and genetic make up passes along our genes, and humans are susceptible to damaging genetic combinations which cannot be weeded out by stronger genetics when there is incest resulting in pregnancy. Wild animals display almost no signs of incestuous relations ships, unlike homosexuality.

Where is the vote for "Neither moral or immoral"?

Morality is a human construct and not readily measured, and context has a lot to do with many "moral" decisions. Children from incest have a larger chance for genetic issues, so it probably isn't the smartest choice for a child bearing partner, but if you aren't going to have children, who cares? It is not my business to tally who is fucking who in this world, and I wish everyone else would stop because it shouldn't matter to anyone but the small minded who wish to gossip.