Comparing DNA Results: Three Siblings

I recently concluded DNA testing of my mother’s two full siblings on Having finally tested all three of them, I thought it would be interesting to conduct a comparison of their results to understand more about the similarities and differences between their DNA. This is what I found!

All names and images have been redacted to protect the privacy of the these individuals, who kindly agreed to DNA testing, and their matches. The three children are referred to as Child A, Child B, and Child C according to birth order. Since only autosomal DNA tests were involved, identifying the gender of the children is not pertinent to the results.

Ethnicity Estimates

Child A and Child B have almost identical ethnicity estimates while Child C’s estimates are slightly different. All three indicate a strong background in Great Britain, which is surprisingly not something that has come up in my research. This is probably because all the branches seem to dead end before crossing the pond, but the very few I have been able to trace end in Germany. Interestingly, that doesn’t seem to be reflected the ethnicity estimates, other than a small amount in Child C. This could be because those German ancestors are so distant and so few that they don’t show up in the DNA, or it could be because those ancestors actually had even more distant roots elsewhere prior to living in Germany.


Below is an example of the ethnicity estimate details for Child A showing the range of percentages for each ethnicity estimate. This illustrates why some regions are termed “Low Confidence Regions.” All the estimates, other than Great Britain, are deemed “Low Confidence” because the lowest amount in the range is 0%. The range for Great Britain, while reported at 86%, is actually shown as falling between 71% and 100%.


Genetic Communities

Genetic Communities is an interesting feature that is pretty new to Ancestry. Ancestry has compared thousands of DNA test results against the locations of ancestors in the family trees of test takers to develop a more recent guess of the communities where a person’s ancestors might have lived. They have added historical context explaining why the community might have migrated in the pattern they did, when, and where.

All three children’s results have similar genetic communities, but not exactly the same ones. None of them come as a surprise, they correlate well with my research. The Delaware Valley community generally corresponds to the paternal side of the family for these children, while the Pennsylvania communities generally correspond to the maternal side of the family. Although there is a lot of geographic overlap of the four communities, so there is probably some representation of both sides of the family in all four communities. There is little demonstrated in other aspects of the DNA results to explain the different Genetic Communities each child has been assigned to. I’ll be interested to see if Ancestry adds or modifies any Genetic Communities in the coming year or two and what affect that has on these results.


Delaware Valley Settlers:

Delaware Valley Settlers.png

Pennsylvania, Ohio & Indiana Settlers:

Pennsylvania Ohio Indiana Settlers.png

Pennsylvania Settlers:

Pennsylvania Settlers.png

Susquehanna River Valley Settlers:

Susquehanna River Valley Settlers.png

DNA Circles

Each child is a member of the same 4 DNA Circles shown below. These 4 circles represent two couples: Adam was married to Jane, they were the 5x great-grandparents of these children, and Benjamin was married to Susan, they were the 3x great-grandparents of these children. Both couples appear in the maternal line of the children. The number of people in the DNA Circle is on the left and the number of DNA matches each child has within the circle are in the columns on the right. The varying number of matches for the first couple is significant because it shows the impact of the different size and number of DNA segments each child inherited from these ancestors. There likely isn’t any variation for the second couple because they are more closely related to this couple, and therefore the cousins.

The discrepancy between the size of Adam and Jane’s DNA Circles could be accounted for by the fact that Adam was married twice, so some children would be matches to the other wife, but it could also be accounted for by the fact that females can be difficult to trace. It’s possible that 3 of the 34 people in Adam’s DNA Circle have not identified Jane in their tree at all, or not adequately for the system to identify them as the same person.


Below is an example of what a DNA Circle looks like for Adam as seen via Child B’s results page. It has 34 members that come from different 15 family groups. The family group that these children are part of includes their aunt and is named after their grandmother, Harriet, since she is the most recent ancestor that all four relatives have in common. In addition to matching all their siblings and aunt, Child B also matches only 3 other people out of the 34 people that all three children are almost certainly related to. Among all four members of the group, DNA matches are only found in 4 other family groups, which are shown on the right. Therefore, the DNA Circle has served its purpose in uncovering cousin matches that DNA matching alone would not have revealed.

Adam DNA Circle:



This is just one example of some similarities and differences present in the DNA results of siblings and how the collective results can be interpreted. I have also tested my father and one of his siblings, as well as my grandfather and one of his siblings, but I have not yet reviewed those two pairs of DNA results in this manner. I can say with certainty that in all three cases where I tested groups of siblings, each sibling’s results have yielded new DNA matches that have furthered my research. Each sibling has at least a few distant matches not shared by the others. I will also point out that even when the results are very similar, such as Child A and B here, the consistency between results makes it easier to view small or unusual details as significant and makes it easier to draw generalizations from the results. All of these things have been great for expanding the genetic genealogy work I’ve been able to accomplish using these results and has made the additional tests worth the expense in my eyes.

I will continue the analysis of these siblings when the final test from this group has been uploaded to GedMatch, as well as reporting on comparisons of the other two groups of siblings I tested. Subscribe to or follow my blog if you are interested in seeing more sibling comparisons in the future!

Have you conducted DNA tests on siblings? What similarities and differences did you notice in their results? Tell me about it in the comments, I’d love to hear from you!

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