When First Cousins Marry

RootsMagic
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1

Many of my wider family lived in small isolated villages in the 18th and 19th centuries so it is not surprising that families frequently inter-married. My problem is that I find it impossible to present the information in a way that makes this clear. With any sort of ancestor chart, the inter-marriage is only apparent when I spot the same people turning up in two (or more!) places in the same chart. It would be nice to have a way of flagging this up automatically. At the moment I try to highlight these instances by colour-coding people who married a cousin, but I have to find the occurrence first.

Screenshot 2023-08-08 at 18.20.45
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In this example shown Robert Norman married his first cousin Martha Melhuish. Then his sister Jane married Martha’'s brother, so of course they were also first cousins. In the next generation it gets even more confusing because Robert and Martha’s son married John and Jane’s daughter. So this means that the happy couple were first cousins twice over, and second cousins twice over too! Moving on to the next generation, Mary Jane had 4 grandparents like we all do. But she only had 4 great-grandparents instead of 8. And she only had 6 great-great-grandparents instead of 16.

It would be nice to have a way of presenting these sorts of relationships clearly, either within Roots Magic or in some other way.

2

A useful article on the effects of 1st cousin marriage on a family tree is:

I hope this is helpful!

3

It is helpful. The chart with the swirly pink and blue lines is just the sort of thing I was looking for. In the next few days I’ll prepare a gedcom file and upload it, to see how it works out for my tree. Thanks.

4

And this is what the ancestors of Mary Jane Norman look like using the presentation suggested by GJH.

Screenshot 2023-08-11 at 18.42.42
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Worse than the royal family, and probably on a par with the Habsburgs! (Though not over so many generations.)

5

I created a Custom Fact Type: “Relationship to spouse”:

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6

That’s a nifty idea too. I’ll try that.

7

I wonder if this SQLite query might help your analysis.

Quote from Tom Holden on 2025-07-17, 4:32 pm

I’ve gone through a number of iterations of the query with Gemini and have arrived at the attached script which is

  • some 30x faster than the original I reported,
  • more succinct by listing only the relationship via the Most Recent Common Ancestor(s)
  • more informative by including:
    • names of both MRCA’s when they are the family from which the cousin couple is descended
    • half-cousin relationships
    • number of children for each cousin couple

Here’s a sample output:

FatherName MotherName CommonAncestor RelationshipDescription NumberOfChildren FatherGenerationsBack MotherGenerationsBack total_generations_back
Wyatt Wxxxx-1476 Sarah M. A. Exxxx-1472 Joseph Bxxxxxx-911=Sallie Jxxxx-912 Full First Cousins 0 2 2 4
David Dxxxxx Bxxxx-6512 Mary Bxxxx-440 David Bxxxx-62 Half First Cousins 0 2 2 4
Abraham Pxxxxx-25237 Dixie Axxxxx-27989 Archibald Pxxxxx-5955=Malinda Axxxxx-5951 Full 1th Cousin 1 time(s) removed 7 2 3 5

On a RM10 database having ca 17,000 couples in its FamilyTable, the query returned 294 results in under 9 seconds. The query should work on all versions of RM databases from RM4 to RM10 but has been tested only with RM10 databases.

8

Is there any solution build in in RootsMagic’s charts?