The Siamese violinist

Here’s a famous thought-experiment defending abortion:

But now let me ask you to imagine this. You wake up in the morning and find yourself back to back in bed with an unconscious violinist. A famous unconscious violinist. He has been found to have a fatal kidney ailment, and the Society of Music Lovers has canvassed all the available medical records and found that you alone have the right blood type to help. They have therefore kidnapped you, and last night the violinist's circulatory system was plugged into yours, so that your kidneys can be used to extract poisons from his blood as well as your own. The director of the hospital now tells you, "Look, we're sorry the Society of Music Lovers did this to you--we would never have permitted it if we had known. But still, they did it, and the violinist is now plugged into you. To unplug you would be to kill him. But never mind, it's only for nine months. By then he will have recovered from his ailment, and can safely be unplugged from you." Is it morally incumbent on you to accede to this situation? No doubt it would be very nice of you if you did, a great kindness. But do you have to accede to it? What if it were not nine months, but nine years? Or longer still? What if the director of the hospital says. "Tough luck. I agree. but now you've got to stay in bed, with the violinist plugged into you, for the rest of your life. Because remember this. All persons have a right to life, and violinists are persons. Granted you have a right to decide what happens in and to your body, but a person's right to life outweighs your right to decide what happens in and to your body. So you cannot ever be unplugged from him." I imagine you would regard this as outrageous, which suggests that something really is wrong with that plausible-sounding argument I mentioned a moment ago.

http://spot.colorado.edu/~heathwoo/Phil160,Fall02/thomson.htm

Take Siamese twins (nowadays called conjoined twins). You didn’t consent to this. You simply found yourself shackled to your Siamese twin. And it’s not for nine months. It’s for life.

This is far more invasive than pregnancy. Far more confining than pregnancy. You have absolutely no privacy. Absolutely no autonomy. No control over your own body. You can’t go anywhere without taking your Siamese twin along. Can’t talk to anyone without having your twin overhear you. Can’t have a single moment alone.

I believe there are cases where it’s possible to surgically separate conjoined twins, but the procedure will result in one twin surviving while the other twin is killed in the process.

Would it be ethical for a Siamese sibling to have his twin surgically killed to free himself from his conjoint twin? Suppose the twin doesn’t consent to the operation. The twin doesn’t wish to die.

Still, isn’t his fratricidal sibling entitled to do whatever he wants with his own body? Isn’t bodily autonomy his inalienable right?

Or suppose his twin consents to die for the sake of his Siamese sibling. Is consensual fratricide ethical?  Or is it wrong for one brother to kill another brother, even if his sibling agrees to be die at his brother’s hand (via the surgeon’s scalpel)?

Given how ruthless abortion proponents are, I’m not optimistic about how they’d answer these questions.