Using DNA and Gworks for Solving Unknown Parentage Cases


All my slides are at

23 pairs of chromosomes

Image of painted (SKY) chromosomes - Courtesy of DeWitt Stetten, Jr., Museum of Medical Research

How can DNA matching identify a relationship?

Chart from ISOGG wiki (courtesy Dimario, Wikimedia Commons)

How can your DNA identify a relative?

The amount of shared DNA is a range

measured in centiMorgams (cMs)

display from the calculator at

Step 1: TEST your DNA:

at Ancestry and 23andme then transfer to the others

Upload the Ancestry DNA results to other sites for free to get more matches:

  • MyHeritage
  • Family Tree DNA *
  • GEDmatch
  • LivingDNA (no matches until August 2018)

*$19 for the full tools

Once your matches come in ... (start at Ancestry)

Look through the family trees of 2nd, 3rd, and 4th cousin DNA matches for a common ancestral couple or two.

Build private, unsearchable family trees down from each common couple to find where they intersect and/or someone in the right place at the right time.

This may only get to the great grandparents

Then build the pedigree tree of a candidate parent back to at least 1800

Make sure this tree is private and unsearchable

Add a fake child to that parent and then connect your DNA to it

Ancestry will use auto complete in the name field

Select the pedigree tree you created and link to the fake child

Now wait for the hints and see if they are consistent with your hypothesis

Check the cMs of each match and compare them to the charts

Do they fit your theory?

Are there tools to make this process less labor intensive?

Is there automation for comparing trees to find common ancestral couples?

Collects and compares the trees of your matches into your own private database at

In order to use the tree gatherer you need to be a paid member

Find the app called DNAgedcom Client on your computer or look for this icon

Clicking the icon brings up this menu in a box

DGC needs your silver member account DNAgedcom username and password

You also have to tell it what folder to store the results in

Every person you are working on needs their own account at DNAgedcom but you can use your one paid account to collect the data
Use the GWorks Client (DGC) to gather your Ancestry match data

Enter your ancestry username and password

Select Quicker and Skip Distant Cousins

Once you are logged in, the name(s) of people who have shared DNA with you show up in the profile box, select the desired one in the dropdown

Click Gather Matches, when it finishes click Gather Trees, when done DO NOT click Gather ICW

Now your database is ready!

Clicking on the tree name under the ancestor in Compare All Trees takes you to the DNA match
Having the same ancestor in 3 or 4 trees may not be significant if the trees are all from the same user

If you have a second cousin match with a tree, you could try the mirror tree approach

Better ... See if GWorks can identify which line from the second cousin match is the one

Top ten ancestors in GWorks

From a recent case, here is the tree of a 2nd cousin match - can you find any GWorks listed names in the far right of the pedigree?
The Pratt Cranford marriage has 8 children
Three of them have DNA tested descendants, check the McGuire for clues

3 children


Surname frequency can help you decide which children's trees to build down in an unknown parentage case

So the next step was to look for the surname of Pratt B's wife and then for child D's spouse

Targeted Testing

Child D's spouse's surname is in the database many times, now to get a child of D, a possible parent to test

These are the names of the original Spanish settlers of New Mexico
These numbers for the tree matches scream out ENDOGAMY

Top ancestors for an unknown father case ...

The advice to people with endogamous roots is to wait for close matches, 2nd cousins or better ... Tina had one at each site
23andme match
Ancestry match
9 Sons

We had to build the trees for the Martinez matches

Obituaries are a great source for finding the names and parents of the living

Both of the 2 sons who were in the right place at the right time to conceive Tina are dead, but one of each of their children has tested and now we wait

Meanwhile Julie, a daughter of one of the possible half brothers, tested independantly at 23andme and shares 774cM (about 10%)
As of yesterday, both brothers tests are in!
You can use a half sibling or first cousin match to isolate one side by starring those matches
The m_ file is a useful spreadsheet for tracking your research
You can upload GEDcoms from other sources and add them to your database at DNAgedcom
Some adoption searches end happily - new dad Billy has sold his house and is moving near to daughter Cheryl and his sister in Florida
To learn more take a class at

GWorks for UnknownParentage searches

By Kitty Cooper

GWorks for UnknownParentage searches

Slides for my 2018 Jamboree talk on GWorks for adoption searches

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