The Basics for Solving Unknown Parentage Cases using DNA


Why does testing your DNA help?

You get half your DNA from each parent, about a quarter from each grandparent and so forth if enough biological relatives are tested you can figure this out

Step 1: TEST your DNA:

at Ancestry and 23andme then transfer to the other sites

also test any close biological relatives that will help

Step 2: Upload the Ancestry DNA results to other sites for free to get more matches:

  • MyHeritage*
  • Family Tree DNA *
  • GEDmatch
  • LivingDNA (primarily British, not many matches yet)

*  pay a little $ to unlock tools

Most likely you will need to figure it out from cousin matches

Chart from the ISOGG wiki  (courtesy Dimario, Wikimedia Commons)

The "G" trick

The cousin level = the number of "G"s , else the greats plus one

If you are in different generations take the shorter path and the other is removed by the generation difference

If your roots are deeply American, you may only need to test at Ancestry

Any of these matches may resolve the case for you but proceed carefully

The DNA Adoption has much help, with a match that close contact is your next step ... review their advice here:

Enter the cMs and get probable relationships

This online calculator that gives you the probable relationships is an invaluable aid


With less close DNA matches, the basic methodology to resolve unknown parentage involves analyzing and building the trees of your best matches ...

Look through the family trees of 2nd, 3rd, and 4th cousin DNA matches for common ancestral couples ("pedigree triangulation")

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

This may only get to the grandparents  or great grandparents

Once you have a candidate parent build their pedigree tree back to at least 1800

Make sure this tree is private and unsearchable initially but once you are ready to try it out, you make it searchable so that ThruLines can use it for you

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

Ancestry will use auto complete in the name field

Select the pedigree tree you created and link your DNA test to the fake child

Now wait ... it often only takes a day or two to get common ancestor hints ... see if they are consistent with your hypothesis

Click on each Common ancestor in your match page to view the relationship. Consistent with your theory?

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

Do they fit your theory?

Clicking on a person's name in the list of matches  takes you to the DNA match page

Does this fit your theory?

Next click on the shared ancestor's name in the left hand column box called "Common Ancestors" to get to this view which shows the relationship

Let's look at how this works with an actual solved case.


Tessa was looking for her unknown father. All she knew his surname was Padilla and that it was an encounter in a town in California in a specific year

23andme match

It's very helpful when one parent or a half sibling is tested

Her Mom


Because you can separate out the matches and ethnicity of the unknown parent

What does this ethnic mix tell us?

Hispanic, Mexico or New Mexico

People with endogamous roots do best to wait for close matches, 2nd cousins (or better) ... Tessa had three good paternal matches, one at each site.

23andme match

The surnames of many of the paternal matches looked New Mexican to me (endogamous!)

When I lived in Albuquerque, I learned a great deal about the early Spanish settlers of that area so I was happy to help Tessa find her unknown Dad

23andme match

The 23andme match was the grandchild of (Jose) Pasqual PADILLA sharing 5.1%  

or 368 cMs.


Based on other matches and their ages, the 23andme match was confident that he was the half 1st cousin of the Padilla father we were looking for; that Tessa's grandad was a son of the 2nd wife of Pasqual Padilla,

thus a half first cousin once removed - Half1C1R  to Tessa

The Ancestry and MyHeritage matches shared common ancestors: surname MARTINEZ

23andme match

The Ancestry match - 287 cM - had a tree with just parents. Building that tree in our research tree we found common ancestors with the My Heritage match of 282 cM

Eugenio and Maria Martinez

but they were the great great grandparents of the Ancestry match. Jose, the son of that couple who was the Ancestry match's grandad had several wives and many children - so perhaps another half 1st1R?

Obituaries are a great source for finding the names and parents of the living. This one for Trinidad Martinez from the Albuquerque Journal found the Martinez-Padilla pairing we were looking for

Next task was to see if we could find a daughter of (Jose) Trinidad Martinez married to a son of (Jose) Pasqual Padilla

So did Pasqual have a son named Luis?

23andme match
Ancestry match
9 Sons

Yes Pasqual's son Luis married Teresa Martinez! the daughter of (Jose) Trinidad Martinez

Now which of those 9 sons was in California at the right time?

Only 2 of them 

Meanwhile Julie, a daughter of one of the possible half brothers, tested independantly at 23andme and shared 774cM (about 10%)

with Tessa

Now Tessa showed off her sleuthing skills, she called the librarian of the small town that most of these Padillas were from and got copies of their obituaries and lots of information. Neither possible father was still alive but she tracked down a son of each one of them and talked them into testing

So Julie is either a half niece or a 1C1R

image from Blaine Bettinger's chart 2017

Here are the tests results for her possible half  brothers at Ancestry

Tessa was welcomed into her father's family; here she is with her half brother and half niece

To learn more take a class at

Or join Cece Moore's FaceBook group for adoptees

all images either screenshots or used by permission, note that the relationship images are from Blaine Bettinger's chart 2017

Unknown Parentage Searches Part 1: Rootstech Connect 2021

By Kitty Cooper

Unknown Parentage Searches Part 1: Rootstech Connect 2021

Unknown Parentage Searches I: The Basics

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