DNA testing - how to find out if you are the sole living descendant of a particular ancestor


12 July 2023
Dr Sophie Kay explains a simple way to use your DNA test results to discover whether you are last living descendant on a particular line of your family tree.

Genetic genealogy connects us to biological relatives in the modern day who have inherited the same segments of DNA from a shared ancestor or ancestors. We therefore need other descendants of a particular ancestor to exist in the first place for there to be any hope of them showing up on the major genetic databases.

If you are the sole living descendant of a particular line then there may be nobody else to match to – but how to diagnose this?

Return to your traditional (paper-based) research on the line of interest and identify the siblings of your direct-line ancestors (up to, say, 3x-great-grandparent level). Produce these collateral lines forwards using traditional research in records such as:

  • Wills and probate records;
  • Civil registration certificates;
  • Newspapers – including marriage announcements and obituaries;
  • Electoral registers.

Observe how many children there are at each generation – and what happened to them. If the collateral lines from your branch of interest have consistently small families, or do not go on to have children of their own, then the line can die out.

Want to know more about working with DNA? Join the Family Tree DNA bootcamp, starting September 2023 and enrolling now!

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Consider the imprint of major historical events too: if the young people in this branch’s collateral lines suffered a high death toll during wartime, this can also result in you being the sole living descendant. 

Sadly there’s not much you can do to remedy this by working only with autosomal DNA, but triaging the problem is a great sanity-check and helps you understand that absence of matches.

Read Dr Sophie Kay's in-depth 'DNA first aid' article in the August 2023 issue of Family Tree magazine, available here.

About the author

Dr. Sophie Kay is a professional genealogist at Khronicle  and an AGRA Associate, with over 17 years’ experience in family history research across the British Isles. She is the Ancestry and Genealogy Expert for TimeTeam; the DNA & Genetic Genealogy tutor at the Institute for Heraldic and Genealogical Studies; and tutors courses in historical maps and research methodology at Pharos Tutors. A qualified research scientist from the University of Oxford, she is also trained in DNA extraction, genetic analysis and Latin translation. Sophie also loves to pique people's interest with historical occupations and runs the #OccupationOfTheDay hashtag on Twitter, where she showcases mush fakers, leggers, pulpit men and steeplekeepers, to name just a few!