I think you mean Whatever you do, Surreal…stay away from YOUR sister! 
What gets me is that I KNOW these guys who wouldn’t touch or think of their sister all have the hot twins fantasy. You think some girl would do you and her sister at the same time but you won’t think of your sister in that way.
Huh. Shows what you know…
I don’t know about “ick”. It sounds more tragic than icky to me. It’s definitely unfortunate about the kids if any genetic yuckiness has gone on with them, and it was certainly selfish of the parents to risk their children’s health in that way, but overall I think it’s sad as opposed to gross. For anyone who has a SO, imagine if tomorrow someone informed you that he/she is your sibling, and that’s it, you can’t be with that person anymore. Can you imagine? I don’t know if I would be able to end the relationship I’m in based on that info, I am just too in love to really give a crap.
I think I have to agree with Surreal here, to a degree. Sure, there’s the genetics issue, but if you remove the idea that the only reason to be in a relationship is to procreate, then why should we not support and encourage a brother and sister in love just as we would any other couple? I know lots of committed couples who have no desire to have kids, and in several of those cases have taken permanent precautions against the possibility. Nobody looks down on them or thinks they’re gross, so why should it be any different if one of those couples who will never reproduce happens to be siblings?
I know nobody has really said they have a problem with others doing it, just that they themselves don’t find it an attractive prospect, but it seems like most people (I mean in general, not specifically anyone here or anything) think it’s disgusting, and I don’t really get that. No, I personally am not attracted to my own sibling, but as far as I can see, two adults in mutual agreement ought to be able to do anything they want to do, so long as nobody is getting hurt.
I am uneffected by the incest taboo. I’ve got two sisters, and would have sex with either of them. But I also have a very casual attitude about sex in general.
I almost got a chance to have a pair of sisters, but could never get them both drunk enough at the same time, oh well. >:)
It’s funny how people always talk about how important it is for couples to ‘have a lot in common’, but in cases where they really do have a lot in common, such as growing up in the same house together or sharing the same parents, everyone’s opinion changes all of the sudden. Interesting.
My very attractive younger sister was two years behind me throughout school. I must say we each got a great deal of sexual gratification out of the setup. BUT: It came from her fixing me up with her friends and me returning the favor to her with my friends. 
The thought of any sort of physical relationship with her never entered my head, and I’m quite sure it never entered hers either.
If anyone would like to see the subject dealt with in an interesting manner, check out the following good movie: Lone Star (1996) with Elizabeth Pena and Kris Kristofferson.
Surreal: I think you should check out Ol’Gaffer’s first post very closely. It explains what you seem to be having such a difficult time grasping.
Not wanting to have a physical relationship with your sister isn’t a deliberate decision one makes. You simply Don’t Want To Do Her. Since you don’t have a sister yourself, you’re going to have to take what those of us that do have sisters say at face value, or check out research similar to what that O’l Gaffer cited.
Thanks.
I read Ol’Gaffer’s post and the possibility of a ‘Westermarck Effect’ seems to make sense, but the problem then is how do you explain the experiences of NotBob13, Zebra, AHunter3, and Arcite?
I know a guy who once told me he lived out this fantasy. He found it better then a usual menage et tois (however you spell it) becuse they refused to touch each other, and could devote all their attention to him.
That said, I can see how girls find my brother attractive. He is kinda good looking in a tall dark and handsome way, has his own car and has some spending cash. All good things for a 16 year old in the dating game. I’d never think of doing anything with him though because… well like it’s been said. The idea is icky to me, that and I remember the brat I beat half to death a few times. (Well not literally but you get the idea) One of his friends on the other hand… wowza. I’d jump him in an instant if he weren’t four years younger and already dating someone.
And I have found at least one of my cousins attractive. (Well second cousin… son of my Dad’s cousin) He’s pretty hot but I only see him once every few years. It was weird at the family get together. I met a number of cute guys, most of which were related to me slightly. Except for the son of my Great Grandma’s friend… but I didn’t find out he wasn’t related until after the dinner (when we had everyone who was related and descended from each of Great Grandma’s children stand up) and by then it was too late cuz he took off right away.
My brother’s a definite cutie. I’d probably be attracted to him if he weren’t my brother. But as his sister, I’ve just never been attracted to him. I don’t know why; it’s just never been an issue.
I’ll repost what I wrote in a much older thread.
I’m adopted. My birth mother and I recently found each other. A few years after I was born, she married my birth father. They had more kids – two sons and a daughter. I have blood siblings that I never knew about until about eight months ago.
I’ve got pictures of the entire gang, my lost family. My biological sister is “hot”; we’re talking a popular kid in high school who was almost prom queen. (My biological mother is also very attractive. Gee, Mom, thanks for not passing those genes down to me. 
) Anyhow, some long-dormant instinct kicked in, making it nearly impossible to see my biological sister in a sexual manner. I just can’t. I see many of my features in her face, reinforcing that “dear sweet Lord, no way” mindset.
Ahem.
This might have been said before, but here it is again:
If you grow up with someone who is attractive (I myself have a “cute” brother), this doesnt mean you have to be attracted to them. If you live in the same house with someone, you also see all thier bad sides.
…and maybe its a good thing you have no sisters, eh?
Well in my case that’s easy, I’m a pervert.
I guess I should tell the story of my grandparents. My grandmother was adopted as an infant. My grandfather was two years older than she. She was adopted into his family and they were raised in the same house. Obviously they got married and they had a mess of kids. I can’t say how they were raised. I don’t know if their parents told them they were brother and sister or if they reinforced that she was adopted. I should also point out that they grew up in a very small town so the pool of prospective mates would have been small.
Not to hijack this thread, but I don’t want this nugget to go unchallenged.
If this were correct, then there would be no homosexuals. However, since we’re still here, homosexuality must not be an evolutionary dead end. BTW, I’m gay and my ex-wife is lesbian. We have a son, so homosexuals can, and in fact do, “reproduce”. Homosexuality doesn’t affect our ability to reproduce. And based on the number of gay parents I personally know, it doesn’t exactly hinder the propensity to if the desire is there. If you want a deeper discussion of the issue, I’d suggest checking out Esprix’s Ask the Gay Guy (Part I, II, III & IV) series of threads in GD or even start a Gay Parenting thread.
Thanks, Homebrew!
Esprix
Hey everyone. I’ve been out of town since last Thursday and had a comment.
In my original post, I mentioned that “there tends to be less sexual interaction, higher rates of divorce for those that do marry, and lower rates of reproductive success.” Please note that these are only trends and not absolutes.
Within any given population there will be a range of responses. In fact, if we were to poll the entire SDMB, I think that the results would be more in line with what we all anecdotally suspect - the vast majority of people avoid sexual contact with close relatives.
Every now and then, I get a wild hair, and research this topic. I found this thread, and registered just to share this story in hopes of 1) answering the question in the affirmative, and 2) maybe getting some insight from some that did not answer.
My wife has a younger brother that was born when she was 10. Their mom is a piece of work, and pretty much left the day to day raising up to her. Once he was big enough to stand, she would often be handed ‘the baby’ to wash while she was in the shower. This continued until he was 5, and I have seen first hand how he looks at her 34D’s. I am a voyeur myself, and can spot that in moments
Fast-forward a few years: She and I had been married about 8 years, and we both enjoy taking pics and making home movies. Most of them are on my computer, but a couple of movies and about 100 ‘action shots’ of us were on her computer at the time he came to visit us. We both had to work, and she let him use her computer. Neither one of us even considered what was on her HD.
I am an IT guy in the information security field, and am a little paranoid as a result I had her computer setup to audit access to those files, and send alerts to mine if they were accessed. The day he left, I came home, got on my computer, and saw that every file in that folder was accessed at least once. With a little discrete research on her system, I found that after the viewing session, there was a 15 minute break with no computer activity, before he logged into his email.
So, I would toss this one into the Yea category. I’ve never said a thing to either of them, because I don’t want to introduce any tension. I don’t let him on any of our computers though, and check the network shares before his visits now.
It might help if you didn’t get your ideas about how teenage girls behave from 80s teen comedies and softcore porn.
Zombies will eat their sisters with no hesitation.
So get them from hardcore porn, gotcha. Thanks.
A couple other reasons for lack of attraction would be 1) they have “the family forehead” or whatever other physical trait that sets apart your family as something less than attractive in your eyes, and 2) you fought with them for everything and seen their bad side throughout the years so sibling rivalry dampens any attraction.