Using tree building from DNA tools: DNA2Tree and Genetic Affairs to Solve Unknown Parentage Cases


All my slides are at

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

Any of these matches may resolve the case for you right away but proceed carefully with contact

Enter the cMs and get probable relationships

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


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

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.

Build private, unsearchable family trees down from each common couple to find where they intersect to 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 about 1800

Make sure this tree is private and unsearchable initially but once you are ready to try it out,  make it searchable so that Ancestry's 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 to get common ancestor hints ... see if they are consistent with your hypothesis

Select Common ancestors on your match page plus whatever group you are working with. Consistent with your theory?

In this case our entire set of 4th cousins in the BUGDEN group got common ancestors. I like to note the relationship to see if the numbers work

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

Do they fit your theory?

Is there a faster way to check them?

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

Using the Genetic Affairs tree building feature is a faster way to look to see if the centimorgan amounts fit



Close up of the Genetic Affairs tree diagram


Or you can use the "What Are The Odds" tool at DNApainter to check your theory - 

Is there automation for comparing trees

to find common ancestral couples?

Or for building trees?

Can collect and compares the trees of your matches by cluster and includes a GEDcom



Finds the common ancestors from your Ancestry matches and builds trees!

Genetic Affairs


DNA2tree is only on iPhones and iPads via a paid subscription but it is a real game changer for unknown parentage searches

clicking on Load Some Matches gets these options

Favorites = starred

Next click on Find Common Ancestors

Here is a sample set of Common Ancestors 

Note the repeating usernames (privatized) 

See what happens when you Merge Common Ancestors

Now there are only three lines, with no duplication of user names

Details of the Bugden matches

Click on Graph to see an image

like this

for the

Bugden matches


It did not all fit on the screen !


GGrand parents

Grand parents

Click on Build

then fill out some forms

also you have to tell it whether paternal or maternal side

Click on Build


DNA2tree asks you what to call the tree and then builds that tree on your account at Ancestry


BUGDEN tree at Ancestry built by DNA2tree

Thomas BUGDEN  at Ancestry built by DNA2tree


Notice that only his children with DNA tested descendants are listed


And the two Elizabeths are the same person


So much work is still needed

Thomas BUGDEN  at Ancestry with all his children added by us



BUGDEN pedigree for father's mother, full story here:

You may remember the screenshot from the beginning of this talk.

After we found Elana's grandparents for her, she tracked down a cousin of her father's and got her, Joanne, to test, the DNA fits!

There are two sons of the parents we found for her and Elana is still working on finding them

2. Are there any close matches (1st cousins or closer), figure it out from there

3. Does the genetic affairs clustering and tree builder solve this?

4. If you have DNA2tree, use it to find common ancestors and build a research tree or two

   5. Still puzzled? Run GWorks on DNAgedcom and add trees collected elsewhere

6. Once you have some common ancestors, build those trees down to the present looking for someone in the right place at the right time


1. Use the "Are your parents related" (AYPR) tool at GEDmatch on the adoptee

I have a blog in progress on the new tree features at Genetic Affairs. Here is my blog post on using DNA2tree:


Unknown Parentage Cases using Automated Tree Building -i4GG 2020

By Kitty Cooper

Unknown Parentage Cases using Automated Tree Building -i4GG 2020

Automated tree building tools like DNA2tree and Genetic Affairs are making many unknown parentage cases much easier to solve. These are game changers!

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