Dave Obee       Local History / Family History



DNA: Should siblings test?

We get our DNA from our parents. But siblings do not receive exactly the same DNA -- the distribution is more random than that.

After a bit of begging, my two sisters agreed to do an autosomal test through Ancestry. I also tested there (along with other companies). Was it worth it? Yes, without a doubt. The proof is in the numbers.

As I write this, I have 145 fourth-cousin-or-better matches and I have confirmed the relationship for 43 of them. One sister has 205 matches, and I have confirmed 45 of them. The other sister has only 145 matches, but I have confirmed 44 of them. Both sisters have unique matches -- matches that I don't have, or that the other sister does not have.

In reality, each one of us has a few unique matches, ones the other siblings do not have. By testing my sisters, I have added (at this time) almost a dozen new matches -- and every one is a potential lead for further research.

I have also put my top 100 matches into a spreadsheet, along with the top 100 from my sisters. That is a good way to count the unique matches, and the result was amazing. One sister has 54 matches that I do not have. The other has fewer, but still, between the three of us -- DNA confirms we are siblings, by the way -- my top 100 list grew to almost 200. Every one of those matches is a match for me as well.

I have also asked cousins to test. I added to the spreadsheet all matches that are shared between any two of us -- my cousins and my siblings. That took the total match count to 250. The cousin tests have another benefit as well; they can provide clues whether a match is on my father's side or my mother's.

Back to siblings. Again, siblings don't get all the same DNA. DNA from three or four generations might have trickled down to one or two of us, not necessarily all three.

There are other reasons, X and Y, to get siblings to test.

My sisters cannot do a Y-DNA test; only males can do that. The Y chromosome is passed from father to son, so it traces the male-male-male line back. It is a great way to confirm the father's line. Women interested in their family history should ask their brothers, or failing that uncles or their sons on the relevant lines, to do Y tests to collect that information.

Also of interest is X-DNA, referring to a chromosome that cannot be passed from one male to another. My X-DNA information comes from my mother, and I can work back through my charts, eliminating all of the father-son relationships because X cannot get through that wall. X can be used to isolate a potential match to a particular line.

My sisters got the same X-DNA information that I did, but they also got X-DNA from our father, and from his mother, and from her father and mother, and so on. In other words, the tests done by my sisters open up more potential for matches that would apply to all three of us. If a new match is an X match to my sisters, I can check the charts to see which people might be the connection.

Don't have sisters? Check the charts for a cousin who might help.

And yes, X-DNA works. I have found matches on our mother's side as well as, thanks to my sisters, our father's side.

DNA works. It is revolutionizing genealogical research. Start working on it, buy tests for your siblings as well as yourself. Do not delay -- I have learned that that hard way.

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