Three months ago, on 16 August, I wrote a short blog post about a new Facebook group called ‘Cornish Emigrants – GEDmatch Ancestor Project’. Since then the group has grown rapidly, to 599 kits on GEDMatch and 292 members on Facebook.

The aim of the group is to help people research their Cornish family history. To get the most from it, you should already have some well-based knowledge about your Cornish ancestors. If you join only because your DNA tests report likely Cornish ancestry you will probably find that it won’t help you much. You need to have done some research about your Cornish connection.

You can join through Facebook or directly from GEDMatch. On Facebook you give your GEDMatch number and information about your Cornish roots.

The group spreadsheet lists the kits of those who have joined, in kit number order, with details – where these are known – of Facebook name, username, and Cornish surnames associated with the kit.


The first step is to log on to GEDMatch and go to the Ancestor Projects page. Run the report with your kit number. I usually do this with matches > 10 centimorgans (cM). The default setting is > 7 cM, but this can produce matches where the relationship is too distant to trace or where the shared DNA is not genealogically significant.


The GEDMatch home page showing the reports I most frequently run: orange arrow is Ancestor Projects; blue arrow is One-to-One Autosomal DNA Comparison; green arrow is People who match both, or 1 of 2 kits




You then take a screenshot of the report and post it to the Facebook group. If you find correspondences between people in your tree and in the trees of other people in the group, you tag your matches in the post. This you do by typing the @ symbol in the post and then start typing the name. You then choose from the people who pop up in the list. You add the screenshot to your post by selecting the green picture icon shown at the bottom of the screen.


Not all matches from the Cornish Emigrants Ancestor GEDMatch group are on Facebook, for some people join from GEDMatch directly. You will have to email these matches yourself.

To get the most out of trying to connect with others, it is a good idea to upload your tree to GEDMatch. If you find correspondences it will be worth looking at the trees of the people where your matches occur. The tree icon on the GEDMatch report shows if your match has uploaded a tree to GEDMatch.

If the match is a Cornish Emigrants match, I look at any Cornish ancestry in both trees. The connection, of course, might be from some other part of our familys’ ancestries, not necessarily Cornish and/or not displayed on these trees.

I also look at DNA Painter to see if the shared segment is one I have already painted and for whom I have identified an ancestor. This might give me a clue as to where our connection occurs.

DNA_Painter___Profile_-_Greg_Young chr 8 detail

Example of the detail from DNAPainter looking at segments already identified associated with particular ancestors


I run the GEDMatch report of people who match both kits, and look to identify shared matches where I know the connection. (See screenshot above of GEDMatch home page and report identified with green arrow.)

GEDmatch report of both kits

GEDMatch of report of both kits. If I can identify a shared match then I start to have an idea about where on my family tree I should be looking for common ancestors with the other kit.


If my match and I both tested through AncestryDNA then I use the tools on that site to explore the connection, if there is one, between our family trees and to review our shared matches. I also do this with FamilyTreeDNA and MyHeritage. The different sites have different tools, but all of them allow you to review shared matches and family trees
that have been uploaded.