Long story short, a thousand years ago a man killed himself halfway through a ritual, which stopped it in half (think Jumanji). In order to complete the ritual, the bad guys need the direct descendant of the original (his wife and kids survived). How can I make sure that there is only one direct descendant after 1000 years?

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    You should probably ask either on WorldBuilding, Biology, or Genealogy. biology.stackexchange.com genealogy.stackexchange.com We can help you figure out the symbolism of the ritual, or how to develop the language which is used to cast it, but begats aren't our division. Commented Apr 28, 2017 at 19:35
  • The simplest thing i can think of is - Maybe the ritual put a curse on the man's lineage, since it was half finished, that he would only be able to sire a single son and none else until the ritual is completed, as a way to get itself completed....you may need to work out some other details but this should work for your scenario...
    – user96551
    Commented Apr 28, 2017 at 19:47
  • Relevant: english.stackexchange.com/questions/61559/… Commented Apr 29, 2017 at 21:26
  • I think this is probably going to be closed, since questions asking what to write are off-topic here. But as per @LaurenIpsum's comment above, have asked if any other sites feel it's on-topic for them. Commented Apr 29, 2017 at 21:27
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    Have closed as a question asking what to write, but please consider asking this on Worldbuilding; they've expressed some interest in having this question there. Commented Apr 30, 2017 at 18:30

4 Answers 4


John does the ritual. He has several kids.

Maybe most or all them die before having any children of their own.

Even if they do, heck, they can can all die off, even three or four generations in. It CAN just happen to shake out that way.

Certainly possible. Absolutely. But narratively, there isn't any real reason to go into the hows and whys of the fact that there's just one person left in the world that is his direct descendant, unless it adds something to the story.

I would say, that if you do want to get crunchy with it, or you have to absolutely know the mechanics behind it, you should follow other poster's suggestions and ask another board. Don't mention it's for a story, just ask the question: "Is it possible for a man born 1000 years ago to have just one descendant living, given that the man had 5 [or however many] children? Are there people walking around right now who are, so to speak, genetically unique in this respect? I know things can get exponential with generations and just wanted to see if this was plausible in any way, and how it might work?"

It's an interesting question.


Don't even worry about it. Just mention that "Doe was the only direct descendant of Smith." No reason for the reader to do any math.

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    I'm into genealogy. It's amazing how you can go back to medieval times and see a thriving medieval family with lots of children only for, a century later, wars, plagues, economic alliances (marrying cousins and nephews to keep properties together will put a damper on your reproductive ability eventually) or just bad luck will take the old nobleman's lineage into a male dead end. Or plain dead end, if they can't even pull off daughters. To end up with only one direct male descendant is not very difficult. Although it is much easier to end up without none. Commented Apr 29, 2017 at 13:26
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    @SaraCosta Indeed. And I should mention that "direct" descendant implies more than just merely being in the reproductive line. It implies legal (or community) recognition that someone in each generation is some kind of inheritor of rights from the previous generation. Not necessarily sole heir, but still, some kind of general recognition of the link is expected.
    – user23046
    Commented Apr 29, 2017 at 13:59

This is a rather complex answer. Since you did not specify how prevalent magic is, so I'll assume fairly low magic.

If you look for paternal descendants, then having mostly daughters will solve your problem. If the descendant needed can be of either gender, then the BBEG could have been trimming parts of the family over the years. Over centuries, humans spread out across the land. Think back to your own family a thousand years ago... heck even a century ago... Where did they live? What about their own siblings?

Since magic can be factor, perhaps the family have a mark that passes from one generation to the next, perhaps they have a special hair or eye color?

How does the BBEG keep track could provide help. Was he watching over the family from afar? From nearby?

Not a definitive answer for sure, but hopefully some avenues of thought for you to investigate...


The family gets religious, of some sort, which states that you can only have one child, and if it is twins the weaker must be killed.

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