I heard it said all the world leaders are related to royalty , all the presidents having the same bloodline . So if that is the case wouldnt they be interbreeding and having incest relationships to keep the bloodline pure?

No point in safe sex with a relative. Stupid question. Only reason to have sex is breeding. Unless every other woman on earth is dead there’s no moral or any reason to breed with a relative. Only to repopulate. Seriously, this is a disturbing question. I argue, should I let you all die since you’re not smart enough. To figure this out without help. Maybe we should let sea life like octopus’s take over, humans in general seem quite stupid to me. Wtf you even as this for you know the answer. My god the world is dumb and blind.

How is this a question? It happened in the Bible it was condemned. Maybenif last two humans on earth and you need to repopulate but even that’s fucked. I’d clone first. Sick question...

There is incest in most species.

Neither. Incest takes place in many societies and over 400 animal species. Is first cousin sex/married incest? Hundreds of societies do it. Best to avoid it in the immediate family for emotional reasons.

I find this gross because i was raised to believe it is gross. People are taught from birth what is moral or immoral . There is no answer to this question because morals are derived from cultural and society upbringing. Incest occurs in the animal kingdom

It is an Ethics issue. That is just not good for Civilized people to be doing.

NO. This argument leads to one thing. Making it ok to abuse children by grooming them for years to be sex partners. Its grotesque.

CONSENSUAL, SAFE sex is nobody's business but the the participants!

Because my Family Tree should Branch!!!!

havent studies shown that it always leaves people worse off even if no kids are produced?

JUST WRONG! Why do you think their kids have birth defects!

If for any other reason, aside from the birth defect/health issue, I just find it disgusting and unnatural. I can't imagine this occuring between people who weren't at least pretty sick in the head.

I couldn't vote because the question is particularly skewed and unclear.
First I would need a working definition of morality - are we talking about wellbieng or something else?
Are the siblings thinking adults of an equal standing who can make an informed decision of consent?
And why is the question specific to brother and sister? What about brother and brother or sister and sister? Or even brother, sister, brother, brother and sister for that matter.
Several posters have highlighted concerns about the possibility of birth defects in the event of unplanned pregnancy, but I feel this is just a distracter from the initial question and allows an emotional response and not one based purely on logic.
If you take the view of some religions that sex is purely for procreation then it is probably unwise to breed with your siblings.
If you think that sex between fully consenting adults just for pleasure is acceptable, then I see no reason why sex between siblings should be considered 'immoral'. Our socialisation and the norms of the societies in which we live will impact on our yuk factor and make it difficult for us to think rationally on such emotive issues. Probably not much different than asking a Christian why they believe in God.

Because it's gross to bone your sister, it's your sister, like you shouldn't view your own family as boneage material.

I wasn't sure just how to answer this question, but after serious consideration, I can find no scientific reason why 2 consenting adults should not have safe sex.

I think our society has deemed it immoral. But, personally I would think if each was of the age of consent and were not trying to have children, I see no logical reason to claim it's immoral. I think under those strict circumstances it's amoral at best. I'm sure that's not a popular view. But if it offends you, ask yourself why and if it's solely because how you were raised and/or the societal mores within which you grew up.

It's wired right into our DNA to not find a sibling atractive as a sexual partner. It's a bad idea. Condoms are pretty effective but not 100%. I'm going with its not for me but in not going to judge you for it.

Genetically, as stated, it is not advised. Morally... to each their own. I find it repugnant personally - although I must say Oedipus and Jocasta definitely had it going on...

I personally find it gross but what consenting adults do in their bedroom is not my business. With that said, I thought I'd mention something I learned in school a few years back that I found interesting. They did a study where they took people and gave them a shirt worn by a member of the opposite sex to smell. Not surprisingly, straight men preferred the smell of shirts worn by ovulating women. All in all though, we prefer the scent of people whose genes are not similar to ours. Mother nature has built into us an aversion to people with similar DNA, morality be damned

I think you have a moral obligation not to risk birth defects. Inbreeding is the leading cause of it. We've known this since the Egyptians.

Inbreeding causes many biological problems, like genetic disorders and lower IQs.

How is this even a fucking question? NO it is not okay to fuck your kids!!! We don't need an invisible man to have a moral code.

Logically the only thing wrong with incest is it leading to children that would suffer for it, however, I would like to point that there is a lot of cancer in my family and I am perfectly legally allowed to have children with a man that also has a lot of cancer in his family.
I could be told by a doctor that there is a 99% chance if I have children that they will get cancer and yet I can still do that without anyone thinking ill of me for it.
People with mental disorders have kids with other people with mental disorders.
Small People that know they are going to have Small children. (I hope that's the non-offences term for them)
Or any number of other problems.
If you say you can't have kids because they may have problems with their health where exactly do you draw the line?

Biologically, it's not moral or immoral, it just isn't a good idea. As biological creatures, we have been genetically conditioned through evolution to be repulsed at the thought of incest in order to diversify the gene pool, and to avoid those genetic abnormalities that can occur for lack of diversity. When those of us shed the skin of religion, we begin the act of redefining everything in tour lives in terms of morality, but the taboo of incest is a tough nut to crack but of the genetic conditioning the species has gone through.