Genealogy can be fun and rewarding, but it can also be frustrating when you encounter problems that don't seem to make sense. What do you do if your family member's DNA doesn't seem to match your own? Legacy Tree Genealogists' Adrienne Abiodun explains how you can solve this all-too-common problem.
The Problem
Most of us who have taken a DNA test have experienced the startling discovery of NOT having a biological relative, close or distant, known to be related to show up as a genetic match. While jumping to conclusions and thinking the absolute worst is a natural reaction, taking a step back to assess the data or lack thereof may save you unnecessary confusion and heartache in the end. Siblings, half-siblings, aunts, uncles, nieces, nephews, first cousins, second cousins, and other immediate relatives should always share enough DNA to appear in genetic match lists across all major DNA testing sites. However, third cousins, first cousins, and second cousins that are two or three times removed may not always show up as a match.
For simplicity’s sake, let’s consider an example of third cousins. On average third cousins will share approximately 0.98 percent of their DNA, which is about 73 centiMorgans (cM) of DNA. Their shared DNA is inherited most recently from a great-great-grandparent or pair of second great-grandparents. From an individual standpoint, the amount of DNA one could have likely inherited from a great-great-grandparent is 6.25 percent, which is approximately 425 cM of DNA. Each ancestor generation backward, the amount of DNA inherited is reduced along with the potential of sharing DNA with known third, fourth, and more distant cousins.
On a recent complex client project, a non-match between two individuals who were supposed to be third cousins raised suspicions about their proposed common great-great-grandparents. If they did not share DNA, were they full third cousins, or could they be half third cousins? Were they even genetic relatives at all? A further investigation ruled out this last possibility but was insufficient to differentiate between the first two possibilities. Though they did not match one another, they both shared DNA because both matched with another relative from a third child of their most recent common ancestral couple.
Using the illustration below for reference, one can see a great-great-grandchild number one and great-great-grandchild number two were not genetic matches to one another. However, they are known proposed paper-trail third cousins to each other. Both matched grandchild number three and great-grandchild number three from the same common ancestor and shared an appropriate amount of DNA with those matches for their relationship types as first cousins twice removed and second cousins once removed, respectively. The most recent common ancestor pair would involve a marriage record that has yet to be found, a move from Finland to the United States of America where some children were born in Finland and some in the United States. The situation raises questions about whether child number one and child number two were half-siblings rather than full siblings.
In a situation like this, targeted DNA testing strategies were suggested and applied. A great-grandchild of child number two was invited to participate in DNA testing to determine how they would compare to genetic descendants of both child number one and child number three. Their DNA results were added to the analysis, resolving concerns regarding the genetic evidence. All three children of the most recent common ancestor(s) were, in fact, full siblings to one another. It also reinforced how third cousin matches may or may not share DNA. The relationship between the great-grandchild of child number two and great-great-grandchild number one is the second cousin once removed. The average amount of shared DNA for this relationship type is 1.64 percent or 122 cM of DNA. They shared 113 cM, which was very close to these observed averages.
In similar scenarios like this one, targeted DNA testing of additional individuals understood to be related to both DNA tested subjects in question is always encouraged when possible. But what if targeted DNA testing isn’t available? Here are some other strategies to consider for understanding your genetic non-match to your relative.
The Solution
- Remain calm and attempt to refrain from jumping to negative conclusions.
- Determine whether you have calculated your relationship with one another appropriately. We will often hear two cousins refer to themselves as second cousins to one another when they are second cousins once removed, third cousins, or something entirely different from a second cousin. While it may all seem the same, in the game of DNA matching, precise relationships matter. Chart yourself and your cousin’s connection to one another and use relationship tools on sites like DNA Painter to understand removed relationships.
- If no test candidates are interested or available to pursue targeted DNA testing around the two individuals in question, sharing DNA match lists with your non-match to compare matches in common may also be sufficient. When sharing lists, observe whether you both have matches from your most recent common ancestor(s) and matches coming from both sides of your most recent common ancestors’ families. Evaluate whether the amounts of shared DNA with your in common matches is appropriate for their relationships to you and the distance between them and your most recent common ancestor.
In summary, it is essential to remember precise relationships matter when we incorporate genetic genealogy into our traditional genealogy research. More times than not, collaboration among your matches and non-matches is the key to successfully comprehending the data you do and the data you do not see.
DNA research can be difficult to understand, even with the right tools and resources. If you run into a problem you can't solve, our genealogists will work with you to find the solution. Contact us today for a free quote!
Resources
The Shared cM Project 4.0 tool v4,” https://dnapainter.com, accessed June 2021.
Autosomal DNA statistics,” International Society of Genetic Genealogy Wiki, https://isogg.org/wiki/Autosomal_DNA_statistics, accessed June 2021.
My sister came up as my first cousin. My parents did not have any brothers or sisters. I have no first cousins and no aunts or uncles. Can you help me explain this?
Hi Juliana,
That’s puzzling, but I’m sure on of our DNA researchers can help you and point you in the right direction. Please fill out the form below for a free estimate on a consultation package or research. http://www.legacytree.com/contact-us?utm_source=blog&utm_medium=reply&utm_campaign=DNA
My wonder mom told me ,I have a brother is out there somewhere but never me all information about him..Only name Shane/Shawn..I don’t know what to believe anymore..
Hi Bryan,
We would love to help you but would need some additional information. Please contact us by filling out the form on our Get in Touch page. We can point you in the right direction and give you a free estimate if research is needed.
My ‘no match’ is slightly different. An ‘expert’ (Art) tells me that all people with my surname are related. I received a DNA kit (my choice of registries) for Christmas. I asked Art whether or not our family was on a DNA registry. He said that there were many using AncestryDNA. I did it, no one from my father’s side listed. Lots from my mother’s side. Art told me my name hadn’t been added to his matches. I bought 23andMe, same results. I’m inclined to believe that my mother may have had an outside interest. Not a problem, just trying to figure it out.
Hi Kevin,
We’ve helped many people in your situation. Please consider filling out the form on our Get in Touch page to give us more information. You may be able to learn something from a short consultation.
Very interesting to read but what to do in the case of unknown parentage. Having found after 63 years of my life the son’s of the man who was married to my mother and done DNA Test with one No Match ?
Francis,
Our researchers can provide the next steps to help you learn more about your family. Please contact us by filling out the form on our Get In Touch page. We can point you in the right direction and give you a free estimate if research is needed.
If I do not have a name for my birth grandfather (on my father’s side who was adopted in Canada in 1946) & have had my father take 2 different DNA tests from 2 different sites, is there still a chance we will not find him?
Jennifer, we’ve helped many people in your situation. Please consider filling out the form on our Get in Touch page to give us more information. You may be able to learn something from a short consultation.
Great article!
Renate, thank you so much for your comment!
I have a female cousin M whose grandfather H is the half brother of my great grandfather C. This cousin M is a generation closer to our common ancestor S her great grand mother and my GG grandmother. I share virtually no detectable DNA with M. I have another cousin T
(same generation as me) and her mother N (who is same generation as M). T and N have GG grandfather and G Grandfather (brother of C) respectively.
M, T and N share significant DNA. I share significant DNA with T and N.
Myself and M share the same common surname at birth as H is believed to be an illegitimate son of S who was a widow when she arrived from Germany with my G Grandfather giving birth 2 years later to H with H taking his mother’s surname.
I am really looking for some commentary of why I have no DNA match of myself and M while matching strongly with cousin T and more strongly with grand aunt N.
Hi Michael, we would love to help but would need some additional, detailed information. Please contact us by filling out the form on our Get in Touch page. We can point you in the right direction and give you a free estimate if research is needed.
My daughter does not match with a great great grandfather and we both have done DNA? We match with the gr gr grandmother. I’m boggled Should I delete everyone she does not match me with in thru lines that are a gr grandparent wise? ty
Hi, Laurie! This is a more in depth question that we could answer for you in a consultation. You can sign up for a consultation here.
I have a 1st cousin matching I never knew I had. It seems there was an eldest uncle I never knew I had from both my grandparents, who then had a son. Neither of these offspring may have known who their biological parents were. For some reason, this is all a bit unsettling!
Hi MimiLee! Yes, finding out about unknown biological relatives isn’t always easy news to receive. Our sense of family is disrupted, and it can be difficult to redefine. Sending you our wishes for peace of mind and heart as you continue your family history journey!
I have a cousin M whose great grandmother S is my GG grandmother and there is no DNA match between M and me. I have a grand aunt N who has a good match with M as well as with me. N’s daughter T with same GG grandmother as me matches with M and me.
M’s great grandfather is not the same great grandfather as N and not same GG grandfather as T and me.
Looking for answers.
Hi Michael!
We’d love to help you out with such an interesting situation. You can schedule a consultation with one of our professionals here.
It took me 8 years to figure out a similar situation which was blocking me from Completing my Family Tree. It took DNA Testing of many more people to prove what I figured out with Cousins from Great Grandparents. The Split in the Bubnash Family is at the half siblings from 3rd Great Grandparents. The half 2nd Great Grandfather had a Granddaughter whom I share 180 Centimorgans of DNA with, and I share 76 Centimorgans of DNA with her daughter. While the same half 2nd Great Grandfather had a Grandson that was a full sibling to the Granddaughter above I only share 28 Centimorgans of DNA with that Grandson daughter,but I share just as múch sometimes slightly more DNA with her children 🤔? It’s proven that 1 side of that branch of the Bubnash Family we don’t share any DNA with. The Aunt that I share 180 Centimorgans of DNA is deceased, and was too far gone in old age before she passed to help build the Family Tree. I used DNA Matches for me,my eldest brother,and our cousins from Great Grandparents. All was coordinated by the paper trail from Church Records and USA Census Records. Immigration Records is unknown since Families that I don’t share much if any DNA with 🤔? Following a Family with the same or similar Surname added the Immigration Records to there Family Tree. Since we aren’t much if any for DNA Matches if I save the Immigration Records to my Family Tree Ancestry says that we need to share more DNA 🤔? What I substituted Immigration Records for were Naturalization Court Records from the Federal Courthouse that documents my Great Grandfather’s year of birth as well as place of birth. His parents are on his marriage Record, and his wife was born in the USA.
Oh, wow! Well done, Tim! Really great sleuthing and use of DNA to help you through a complicated brick wall.
I have the same issue. My cousin M has a Great grandmother S who is my my GG grandmother. Very low if any match of S at all with me. A grand aunt N of mine who is same generation as M matches strongly with me and N.
M and N have the same great grandmother S although the grandfathers are different. Another cousin T the daughter of N matches with S, M, N and me. T and I have the same great great grandmother S and great great grandfather.
hi i was told of 2 other cousin. and we all did our DNA but only 2 of us have a match we have the same G G G Gandfather WHY dont they see me in there DNA match is my great gandfather not to the father i no he should be to
Hi Paul! DNA test results can definitely be confusing! We’d love to help you figure out this mystery. This would be a great opportunity for you to schedule a 45 minutes consultation with one of our expert genetic genealogists. You can schedule your consultation here: http://www.legacytree.com/genealogy-consultation
Shouldn’t my maternal first cousin share the same DNA matches with me? She’s the daughter of my aunt (my mother’s sister).
Hi, Roseanne! We’d love to help you solve this mystery. We’ll need a little more information to help you out. It’s probably best to schedule a 45-minute consultation with one of our genetic genealogists: http://www.legacytree.com/genealogy-consultation
My husband did 23andme; found out he had a daughter he didn’t know about. But, his son doesn’t show on the 23and me results. Does the need to do a DNA test also so we can get the correct results? Thank you
Hi, Rachel! We’d love to help you figure this out! It would be much easier for us to give you a better answer in a 45-minute consultation. You can schedule a consultation with one of our DNA experts here: http://www.LegacyTree.com/genealogy-consultation
This was a really eye-opening post! I never considered the complexities that can arise from unexpected DNA results within families. It’s comforting to know that there are steps we can take to address these discrepancies. Thanks for sharing such valuable insights!
This post was incredibly insightful! I’ve been researching my family history, and it’s been frustrating to encounter a DNA mismatch with a known relative. The explanation of possible reasons for these discrepancies was very helpful. I appreciate the practical tips for how to address the situation—definitely going to try those. Thank you for shedding light on such a common issue!