When you can’t get away from your sibling, how do you get it on?

We’re so fascinated by conjoined twins: There aren’t many of them that live long, and we have technology today that can help to separate some of them. But those who can’t be freed from their sibling have a lot to deal with as they grow up. How do they coordinate simple things like going to the bathroom, eating, sleeping, or even going to a store? The most asked question is about what happens when they want to be intimate. And it all depends on how they are fused together.

How 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.”

One reporter calling about the TLC reality show asked, if Abby Hensel is kissed, will her sister Brittany feel it? The biology geek in me wants to answer that the happy hormones that come from a good kiss probably work their way to both brains. But the student of human nature in me says that, when your sister gets kissed and you don’t, it’s quite possible that the unhappy hormones end up standing at the gate.

From my investigation, I would postulate that conjoined twins probably end up having less sex than average people, and that is not only because sex partners are harder to find when you’re conjoined. Conjoined twins simply may not need sex-romance partners as much as the rest of us do. Throughout time and space, they have described their condition as something like being attached to a soul mate. They may just not desperately need a third, just as most of us with a second to whom we are very attached don’t need a third — even when the sex gets old.

But when a conjoined twin has sex with a third person, is the sex — by virtue of the conjoinment — incestuous? Homosexual? Group sex? Well, it definitely is sex. You can tell, because everyone wants to talk about it.