Have I solved my DNA riddle?

QI’m trying to ‘prove’ that William Adams, born 1822, is the great grandson of Sarah Boulton, born 1719, via her son Joseph. Typing ‘Bouton’ into the DNA match page on Ancestry ( ancestry.co.uk) gives several results. I looked for those without a common ancestor, to avoid getting lots of matches. Then I searched for a link from a different descendant of Joseph and Sarah, otherwise that tree could have the same errors. I found Sarah Bouton, despite not being listed as a common ancestor, and the line in that tree is via a different son – Stephen. Have I managed to solve the puzzle? Martin Cobham

ASearching for surnames in a match list in this way can potentially lead to false conclusions, especially if the matches share only a small amount of DNA (eg under 20 cM). Many of these small matches can either be false or very distant. Ancestry estimates that there is only an 11 per cent chance that we will share enough DNA to match with a specific sixth cousin. However, we have many thousands of sixth and more distant cousins, and as we go further back in time we are all related to each other through multiple ancestral pathways.

This means that the match might well be related through a distant undocumented connection, rather than the ancestor who is identified in the tree. So the AncestryDNA test is best used for finding connections in the last five or six generations at most.

You should instead use the Shared Matches feature at AncestryDNA to place the matches into groups based on common matches starting with the known and working out to the unknown. This can easily be done using the coloured dots to create groups. For example, if you find a match with a known second cousin, look at the Shared Matches to see which matches you have in common and assign all of these matches the same-coloured dot. All of the matches in this group will be related through a single set of great grandparents. Repeat the process for all the other second and third cousins. Each group or cluster will share a common ancestor. You will then hope that one of the clusters will form around cousins descended from William Adams or one of his ancestors. The next stage is to research the family trees of all of the people in this cluster to identify the common ancestral couple. Debbie Kennett

You can use Ancestry’s ‘Groups’ tool to group shared matches with a known second cousin into clusters