Endogamy Success: Finding a Biological Grandfather

Melanie Mohler

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Endogamy can prove to be a barrier to using your DNA test results to build your family tree. But there are tips and strategies that can help you with specific goals, such as finding a biological grandfather. Read about how Anna used skills that she learned in the Endogamy & DNA Course to identify her biological grandfather.

When Anna’s DNA journey revealed her mom’s father was not her birth father, she began looking for her biological grandfather’s identity.

After convincing several of her DNA matches to upload their test results to MyHeritage, Anna (whose name has been changed for privacy reasons) ran her mother’s DNA test results through MyHeritage’s AutoClusters tool. Ideally, the tool sorts her DNA matches neatly into distinct clusters of people who are related on different branches of her family (below left). But what Anna got appears on the right:






“My mum just had ONE BIG CLUSTER–no smaller clusters!” she recalls. “Her highest DNA matches over 100cM just didn’t seem to be connected and/or connecting at the right predicted level of genetic relationship. I was super frustrated!”

Endogamy success story

Because of the one big cluster, Anna suspected endogamy, multiple relationships, or both were affecting her mom’s DNA match list. These scenarios cause DNA sharing among matches from different branches of a family (which is why DNA matches would appear all clustered together instead of grouping nicely into individual branches of the family). But she didn’t know how to adjust for these. So Anna enrolled in Your DNA Guide’s Endogamy & DNA Course.

“My main goal was to REALLY understand what endogamy is and how that differed from multiple relationships,” she says. And of course, to identify that unknown birth grandfather. She credits the Endogamy & DNA Course with teaching her two key strategies:

1. Adjusting shared DNA at each testing company

“I learned how to work with each of the testing companies to adjust the amount of [shared] DNA to get more realistic cM matches,” she says. “This was really valuable, as each site is different. Suddenly my mum’s DNA matches made more sense from a genetic relationship perspective. Matches I hadn’t looked at before because they were below 100cM provided new clues. And…I found my mum’s bio dad and family!”

2. Focusing on the longest shared segment

A number of Anna’s matches below 100cM contained large pieces, but some only shared one piece of DNA and that was between 50-65cM. The course taught her the importance of these longest blocks of DNA— they are more reliable. By focusing in on these discoveries, Anna was then able to re-evaluate her mom’s entire match list in a much more meaningful way. The image below is an example of one of her mom’s matches with 47cM being the largest shared segment.


It was a challenging and a time consuming process, but Anna found some potential matches for her mom’s bio father! Using the WATO tool and genealogy records, she was able to narrow down candidates to only one person who was in the right place at the right time to have been her mom’s biological father. All wins!

Anna’s mom’s DNA matches showed South African endogamy, a mixture of Dutch, French, German, indigenous communities, and other ethnicities. The first European settlement in South Africa was founded in 1652 by Jan van Riebeeck, a Dutch east India company employee. In the first few years there were under 1,000 European settlers living in South Africa, and then for the next four to five centuries many cousins married cousins or half cousins.

Do your matches also cluster together when they shouldn’t? Would you like to learn more about getting started teasing them apart? Join our Endogamy & DNA Course.

Explore the Endogamy & DNA Course

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