From the Atlantic:
One thing we know for sure about the sexuality of conjoined twins: People who aren't conjoined are fascinated by it. At least it seems that way, judging by the number of reporters calling me to ask about the sex lives of conjoined twins since the TLC reality show Abby and Brittany went on the air several weeks ago. As I've told callers, although there are no real studies of the sex lives of conjoined twins, we can safely assume that conjoined twins want -- and occasionally feel conflicted about wanting -- sex, as we all do.
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Sex is often mentioned by commentators on conjoinment as one of the beautiful things supposedly made instantaneously horrible by conjoinment. I'm afraid I just laughed when, in writing a book on conjoined twins, I came across this 1984 line by a nurse writing in a medical journal: "Two people never being able to obtain privacy to bathe, excrete, copulate, or eat defies imagination."
Surgeons sometimes openly allude to sexuality as a motivator for separation surgery. In 2002, as soon as he had made the cut separating two little girls joined at the head, the neurosurgeon involved paused to announce to the assembled medical team, "We now have two weddings to go to." Indeed, when I talked to contemporary surgeons about how they decide whether to undertake the substantial risks some separations involve, I found that surgeons had two fears, sort of conjoined: one, that twins would grow up conjoined and thus never have sex; two, that twins would grow up conjoined and actually have sex.
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So, I suppose I should get to what the people really want to know: what do conjoined twins feel when they have sex? If one is sexually stimulated, does the other feel it? If one has an orgasm, does the other enjoy the same, however unwittingly?
The short answer is that we don't know. Conjoined twins, like the rest of us, tend not to talk in great depth publicly about their most intimate moments. Based on what we know about the significant variability of one conjoined twin to feel a body part (e.g., an arm) that putatively "belongs" to the other twin, it's hard to guess how any conjoinment will turn out in practice. Nerves, muscles, hormones, and psychology all probably factor in to who feels what. If twins share one set of genitals, they're both going to feel any touching down there. Whether or not both are "having sex" with the third person in the equation depends on how you think about "having sex."
Read the whole article here.