Help Collect DNA Statistics

Blaine at the Gorge Wildlife Park, Cudlee Creek, South Australia (used with his permission)

Many families have grandparents or great grandparents who are first or second cousins. Within family marriages did not used to be as unusual as they are today. However for those of us who work with DNA, the extra relatedness adds confusion to interpreting the comparisons of their descendants. Plus there are people whose parents are related. It would be nice to have some charts showing the expected DNA amounts in these more unusual relationships.

Some of you are familiar with the statistics Blaine Bettinger has collected for more ordinary relationships. (Click here to contribute your numbers there) The calculator at DNApainter, which we all use to check the possibilites for an unknown DNA relationship, is based on his research and the statistical work of Andrew Millard and Leah Larkin.

Now Blaine is collecting the data for these more unusual relationships. So any of you who have DNA results from known double cousins or other family members whose descriptions fit, please click that image below to go to the form where you can add your numbers to his new project.


There are more places to contribute your numbers

A long time ago I wrote a post about the Are Your Parents Related Tool at GEDmatch, a tool which looks for places in your DNA test results where you have a long run of identical DNA on each side of a chromosome pair. In other words, you have segments of the exact same DNA from each parent. My theory, which has so far worked in practice, is that you multiply the cM of matching DNA by 4 to get the amount shared by your parents. I will be interested to see how the numbers Blaine collects compare.

Lara Diamond has collected statistics on the endogamous Ashkenazi population, click here to read that. If you have data to add to her survey then click here.

I have been collecting the numbers for 25% relationships (half sibling, aunt, uncle, grandparent, ..) so add yours by clicking here.

I also have been collecting the amount shared on the X chromosome for close relatives which I posted about at


Thanks to everyone who added their family’s numbers!


5 thoughts on “Help Collect DNA Statistics

Click here to add your thoughts at the end of the comments
  1. My sister had our mother, father, her husband, their 2 boys and me (her sister) take the test. I’m happy to contribute information to help the research, but I’m as lost as can be trying to fill out the form.

    • Sharon –
      Make a list of how much DNA each person shares with each other person (I use spreadsheets) then fill out the forms which are relevant for your family
      If your parents were not related to each other then skip Blaine’s new project.
      If you are not Jewish skip Lara’s project
      Please add your aunt-nephew and grandparent-granchild statistics to my 25% project, but if you have only tested at Ancestry then you cannot answer most of the questions, you would need to have everyone upload to GEDmatch and get the segment data from there. Same for my X project

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