In my science fiction story, there are basically two nations that hate each other. There are no contacts between them and they hardly know how life is on the other side of the border.

The protagonist is a young woman who has a twin brother that lives in the other nation. They were separated at birth; they know about each other's existence but they were brought up not to care a lot about it.

Of course, a crucial part of my story requires them to meet. The "government" of both nations would not like it, so there needs to be a very important reason that will convince somebody to help make it happen.

The best idea I can come up with at the moment is a particular genetic disease in the protagonist, that can be cured only with the help of a very close relative. The details about the healing process can be science-fictional, but I would like the disease to be something that exists in real life. Can anybody with a better medical knowledge than mine help?

Edit: I doubt it adds to the question, but since some of you have shown interest, I'll explain very briefly: the two nations are gender based, women on one side and men on the other. Interaction is limited to what is necessary to perpetuate the species... Baby boys are sent on the other side right after birth.

  • $\begingroup$ Did you mean brothers, as per the subject line, or a brother and sister, as per the body of your question? The brothers could be identical twins, which makes them genetically identical, which opens up more medical possibilities. A brother and sister can't be identical twins. $\endgroup$ Sep 12, 2016 at 15:54
  • $\begingroup$ You are right, sorry for my flawed English (in Italian, saying "brothers" doesn't define gender). Indeed, the fact that they are a brother and a sister is quite important. Now the title is fixed. $\endgroup$
    – Giuseppe
    Sep 12, 2016 at 16:03
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    $\begingroup$ OK, that's clear now. The non-gender-specific way in English would be "twin siblings",, and "fraternal twin siblings" states that they aren't identical twins, even if they are the same gender. $\endgroup$ Sep 12, 2016 at 16:19
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    $\begingroup$ If you're really looking for a reality check, there's no way two nations without any formal ties whatsoever are going to restart formal communication over the life of a single person unless said person is super rich or is a leader of one of the two nations. In reality, you'd have an extremely difficult time to just get the government of the US to convince the government of the UK to spend any of their time trying to track down a twin in their country just for some medical procedure needed by a single individual. $\endgroup$ Sep 12, 2016 at 18:09
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    $\begingroup$ When I saw this title on the HNQ I thought that the question was going to be about joining two twins together, as in making them one person... $\endgroup$
    – Mithical
    Sep 12, 2016 at 20:32

4 Answers 4


Organ donation, blood donation and bone marrow donation.

Your best bet based on existing medicine would be to have one of them desperately need an organ donation. Make the 2 of them descend from a very small minority group and note that they have very rare/unusual tissue/blood types.

In that case a close family member like a fraternal twin would be fairly good bet for a match.

I'm not currently aware of any genetic disease with the characteristics you describe.

  • $\begingroup$ ideally it would be something requiring many frequent transplants so they would need to be close for a while. leukemia comes to mind, or any other reason for a white blood cell transplant en.wikipedia.org/wiki/… $\endgroup$ Sep 12, 2016 at 17:45

What about a particular kind of cancer?

I'm not a doctor, but it is my understanding that some kinds of cancer happen due to DNA damage.
What would happen if the two nations had a problem on vast scale of people having these kinds of illnesses? I think they might try procedures to repair the DNA, and since identical twins have the same DNA, they could lead their trials on twins.

Of course, if the phaenomenon is widespread, the governments would have to "use" all the twins possible (since they are rare)...

  • $\begingroup$ Nice idea, but they're brother and sister, and thus not identical... That could be mande into an additionnal twist, though. $\endgroup$
    – Quentin
    Sep 12, 2016 at 15:56

The Re-Unification Project

Your two nations have — like Sweden — a complete blood sample registry of everyone born in that country. In this setting we can even expand it a bit to have anyone ever received medical treatment in any of these countries are in the records of the respective countries. Originally this sampling was done for research purposes... but then people started taking it further.

After a few couple of cases — celebrated in the rest of the world as heart-warming story of re-unification — where siblings or other relatives have reunited, for instance during majors sports events like the Olympics, a computer enthusiast group (that-is-totally-not-Anonymous), have started up The Re-Unification Project. They break into the medical registers of these two nations and copies all the DNA profiles that have been gathered from the blood samples. (*)

Once they start matching up DNA profiles it is only a short while before people across the border start getting messages of the sort "Did you know you have a brother/sister/father/mother on the other side?".

(*) The fact that profiling has taken place is you can make a side-story of, or even have The Project be an off-shoot of discovering that the nations have been profiling the blood samples, which they were not supposed to do. In real life, profiling is something that is a hotly debated matter in Sweden, where I am lending this idea of a national blood sample database from.


Two nations that hate each other will always have spies working in the opposing nation. One of the spies could be one of the twins or be a close acquaintance of one of them. The other one could have access to a medical facility.


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