It’s time for more DNA comparisons! This week I am exploring the Ancestry DNA results of three siblings by examining their DNA matches. If you missed last week’s post comparing some of the other aspects of the same trio’s Ancestry DNA results, you can click this link:
In last week’s post I made the claim at the end that I thought testing all these siblings (at significant expense) was worthwhile because I had found new matches from each additional test. I thought this week would be a good opportunity to back up that claim with some numbers! It’s a long one so grab some popcorn…
To tackle this problem, I went through the first page of each child’s DNA matches, which displays the top 50 matches. For each match on the page I listed the number of centimorgans (cMs) shared with the child and the number of matching segments shared with the child. The first-page matches for each child appear in white in the chart at the bottom of the page. Since I didn’t include the siblings, themselves, in any of my counts, we can actually consider that I examined their 48 highest matches. This includes an aunt and an uncle of the children for whom I also manage the results.
I ended up with a total of 90 unique DNA matches that appear on the first page of one or more siblings. That means the children had some overlap within their top matches, but each one also had some DNA matches that did not appear in the top matches of one or both of their siblings. Let’s break down the match count a little:
- 17 matches appeared on the first page for all 3 siblings
- 1 match appeared on the first pages of both Child A & Child C, but not Child B
- 11 matches appeared on the first pages of both Child A & Child B, but not Child C
- 6 matches appeared on the first pages of both Child B & Child C, but not Child A
Just from these numbers, it’s already apparent that testing only one of the three children would have resulted in missing one or more “top” matches.
With the first round of my list complete, I went back through and identified the amount of shared DNA for each sibling with each match, even if they didn’t appear on the first page for that child. I accomplished this by viewing the match page of each first-page match and clicking on the username. That brought me to their profile page (see image below) where I could select a DNA test I manage and it would either inform me it is a match to any tests they manage or it would say they were not a match. If they were a match I could view the match page and extract the shared DNA amounts, those numbers appear in gray in the chart. If they were not a match I put zeros in both gray boxes.
- 4 matches were on the first page of only one child and had no shared DNA the other two children
- 32 matches had no DNA shared with least one of the children but were on the first page of at least one child
- 24.7 cM is the average difference in the amount of DNA each sibling shares with each of the 90 matches (calculated by finding the absolute value of the differences between all the columns and averaging it)
- 192 cM is the largest difference in shared DNA between two siblings and a first-page match, excluding the aunt and uncle (Child A shares 192cMs more with Match 001 than Child C does)
- 77 cM is the largest amount of DNA shared between a sibling and a first-page match that also has no shared DNA with at least one sibling (Match 067 and Child C share 77cMs, Match 067 shares no DNA with Child A)
Next I sorted the matches from largest to smallest cMs for Child B. I decided to do this because Child B was the first to be DNA tested. This allows me to determine the value added by testing the additional siblings. What I discovered was that, within only these three first pages of matches, there were 23 matches that either would never have shown up on Child B’s match list (0 cMs) or might have been overlooked due to their small shared amount (~15cMs or smaller). These have been highlighted with a red box around them at the bottom of the chart. Of those matches, 15 shared no DNA at all with the original test taker, Child B. Remember, we’ve only examined 90 DNA matches, between the three children there are thousands of matches. This, again, proves to me that additional siblings do bring something to the table when it comes to DNA testing!
Finally, I took a closer look at the group of 23 “added” matches one by one and what I found was that many had potential to add significant value to my research. Below are a few examples of how some of these might contribute to my research (the examples are also highlighted in red font in the chart):
- Match 067 had a very unique surname in their tree that is a huge research interest of mine. I am trying to work on a One Name Study for this surname and it has become a brick wall in my tree. This was a very important match for me that would have been totally overlooked without Child C’s DNA.
- Matches 071 & 083, despite having very small trees, had a particular small town in both of their trees. I am almost certain I know which lines they will connect through if I extend their trees and communicate with them. It could help me get past some periods of poor records that have hindered my research.
- Match 088 had both a surname and location that I recognize in their tree. Getting in contact with them could yield new stories or photos that I have been lacking on this line.
- Matches 070 & 079 have large private trees. Getting in contact with them could open up new avenues for research.
These examples demonstrate that even though many Ancestry matches will have no tree or a private tree, testing addition siblings can reveal some new matches that do shed light on my research.
Although many of the matches in this list do appear somewhere in the match list of Child B, testing the other two children still helped me identify some close DNA matches. Ancestry does not make their match list easy to navigate. With limited search capabilities, limited ability to view shared matches, no option to re-sort the list, the shared cM amount not visible within the list, and now no page count visible on the list, even genealogically close matches can get buried beneath hundreds of pages if the amount of shared DNA is low. Low amount of shared DNA with one child can give the false impression that the match is quite distantly related and therefore not worth pursuing, when in fact the DNA of another child reveals the match is quite closely related. Sifting through page upon page of matches to locate useful information will tire even the most enthusiastic and dedicated researcher. Testing siblings allows some significant matches that would have otherwise been missed to float to the top of the list. This is the power of testing multiple siblings.
Let me reiterate that this analysis accounts for only a small sampling of matches. Imagine going through hundreds of pages where amount of overlapping DNA between matches and siblings become smaller and smaller. The value of testing siblings only increases. Additionally, each sibling has Shared Ancestor Hints, matches with public trees, and matches that respond to messages who are not represented within their first page but are still “value added” matches for my research.
It’s impossible to guess in advance how much value a sibling test will add to your research but the point is that you won’t know until you try it. If you have hesitated to test your siblings, your aunts and uncles, or multiple cousins, I hope you see that there is more to be found from genetic genealogy than what one person’s 23 pairs of chromosomes can tell you. You never know what brick walls might be solved by getting one more person in the family to spit in a tube!
With that in mind, the holiday season is fast approaching and DNA tests will be going on sale soon. My favorite way to buy AncestryDNA tests is to wait for the Black Friday sale. For the past 2-3 years Ancestry has dropped their price to $59 per kit, which is the lowest price of the year (outside of RootsTech, if you’re going to RT definitely buy your tests there). On top of this sale you can sign up for Ebates. If you don’t know about Ebates, essentially you begin all your online shopping trips through Ebates site. If you use their search feature to direct you to Ancestry’s website you can earn a percentage of cash back on your purchase. Typically this is around 6-10%, but often that number will increase, even double, for Black Friday!
Have you ever noticed a difference in DNA matches between relatives? Share your experience with me in the comments!
Behold the Giant DNA Match Comparison Chart:
(If the chart is too small to read you can view the full image here and zoom in on it.)