Genetic genealogist Debbie Kennett explains how she used DNA testing to solve a paternity mystery
DEBBIE KENNETT is the author of DNA and Social Networking (The History Press, 2011)
DNA testing is proving to be a transformative tool, not just for verifying our family trees but also for solving long-standing family mysteries. We also need to be prepared for the unexpected, as DNA testing can throw up surprises. It’s easy to work with your matches once you know how, and case reports are often the easiest way to understand the methodology. I have drawn here on an example from my own family tree to show how, while trying to solve one family mystery about the parentage of my mother’s grandfather, I uncovered instead a long-standing family secret. The techniques demonstrated will be equally applicable for family historians faced with similar scenarios.
One of my goals when I first entered the world of DNA testing was to identify the father of my mum’s paternal grandfather James Lymer Ratty.
According to the censuses, he was born about 1860 in St Luke’s or Bermondsey in London, but I have been unable to find a birth certificate or baptismal record and he cannot be found in the 1861 census. The father’s name given on his two marriage certificates is the name of his uncle. My working assumption is that he was illegitimate.
I was fortunate that my mum was able to take a DNA test, and she is now represented in all of the DNA databases. The first step when working with your DNA matches is to sort them into clusters of shared matches. This can easily be done using the Shared Matches tool and the coloured dots at AncestryDNA (ancestry.co.uk/dna) and MyHeritage (myheritage.com) – see the guide on page 16. Start with the highest match, such as a second cousin, and then assign all of the matches who share DNA with you and your second cousin with the same coloured dot. Repeat the process for the next highest match without a dot, and keep going until you’ve assigned dots to all matches sharing over about 30 centimorgans (cM). The clusters can be given names based on the surnames of the common ancestral couple. When using DNA to identify an unknown grandparent or great grandparent, we are hoping to find a cluster of mystery matches with surnames that we don’t recognise.
With my mum’s matches at AncestryDNA, I was able to identify four main clusters of shared matches. Two large clusters were composed of identifiable cousins related through my mum’s maternal and paternal grandmothers. A third cluster was mad
