Unless you get lucky with a first cousin or closer match, searching for an unknown parent or grandparent involves building lots of trees for your DNA relatives and looking for common ancestors among them. Then you build down from those ancestors looking for someone in the right place at the right time. It is best to have two pairs of common ancestors because then you are looking for where their descendants meet in a marriage.
It is wonderful to have automation to compare trees for you. The GWorks tool suite from DNAgedcom.com does just that and, no surprise, I have written many blog posts about how to use those tools. They can collect all your Ancestry matches and then all the ancestors in their DNA connected trees and give you a list of the most frequently seen ancestors. You can also upload GEDcoms collected elsewhere or created by your own research to use in the comparison.
There are many times I would like to automatically exclude half the ancestors collected from Ancestry. For example when I am helping a person who knows only one parent but has a half sibling or the known parent tested. Specifically when they look at the results from a GWorks run, how do they eliminate the matches from the other side?
One way is to go to the “View Trees” on the GWorks menu at DNAgedcom and delete all the trees from the known side by clicking the red X to the far right of each tree. Then rerun the “Match GEDcom files” in the Manage Tree Files function. This could take forever in a half sibling case.
However, it is very useful to delete trees when one person has tested multiple family members and they are all in the same tree. In that case I keep the tree for the person who is further up the line. Very conveniently you can click on the tree name to go to that match at Ancestry, as long as you are logged in there, so you can easily figure out which one to keep. But again, this is too lengthy a process for a half sibling case.
I have long used the Match-O-Matic (M-O-M) feature in the DNAgedcom client (DGC) to get the lists of matches for just one side (the m_ file) in a spreadsheet for use to keep track of my research. However M-O-M does not work for the tree files (aka the a_ file – actually it has a list of ancestors and which trees they are from).
Sometimes it is good to be a programmer. I have put together a new tool that you can use with a list of matches, for example the match file from M-O-M, to create a new tree file with only those trees that are for the matches in the match file. Then you can upload that match file and the new tree file to DNAgedcom for use in GWorks.
For example, for two half siblings sharing an unknown father you could run M-O-M to get a new match file of just the matches they share. Then use that shared match file with the gathered trees file ( the a_ file) from one of them to generate a new tree file of the trees for the common matches.
The new tool for making tree files is called Extract Desired Lines – click the name to find it with some documentation included:
Are you ready for the step by step?
Start with step 1 in my post about GWorks – – but register a new username for this experiment.
(To create a new email address you can add to your gmail username by using a plus so for example someone+ABC@gmail.com would still go to the someone address as it appears the same to gmail but is a different address to the DNAgedcom website.)
For step 2, collect the match files (m_ files) and at least one trees file (a_ file). If you are working on finding the unknown parent when the half sibling is from the known parent, you need to be careful because they will not share all the same fourth cousins on the known side. For that case, I recommend excluding distant cousins and setting the cM (new feature) to at least 20, perhaps 30 or 40 for the person whose parent you are looking for when collecting the match file, while getting all the matches, even distant cousins, for the other.
The next step (step 2a) is to run Match-o-Matic to get a file with either the shared matches or the matches not shared. Here is what that form looks like. You have to use the buttons to select each match file and then the folder to place the output file, followed by typing in a prefix. Next tell it which file(s) to generate. It runs very fast and does not tell you that it is done, so go look in the folder you selected for files with that prefix.
Step 2b is to run my new tool giving it the M-O-M match file and tree file for the person you are doing the search for. When it is done, you can right click the link and select”Save link as ..” to save that file wherever you wish to. If you just click the link, your browser will probably open it in your default spreadsheet program.
Proceed to step 3 in my GWorks post but use the M-O-M file for your m_ file and the file from my new tool for the a_ file. Soon you will have a database of the ancestors from just the side that you are interested in.
At the beginning of this article, I suggested that this technique can be used to search for an unknown grandparent. To do that, I would run M-O-M repeatedly on all the descendants I had in order to get a list of matches from just that grandparent. Then I would use that M-O-M file with one of the descendants tree files to generate only the trees of interest for GWorks using my new tool.
UPDATE 25-Aug-2018: Thanks to Don Worth we have now named the tool – Tree Slicer for GWorks – http://kittymunson.com/dna/ExtractDesiredLines.php