I am planning to write about all of my experiences soon, but for today I thought I would do a post about my close relatives and just summarize who I asked to take the test and why I wanted them to get tested.
Here is my full sister and how much DNA I share with her as well as the number of segments that we have in common. Siblings are expected to share about 50% of their DNA --- my sister and I share slightly more than expected, just by random chance.
Getting your siblings tested at 23andme is very useful because they will have DNA (and relatives along that DNA) that you do not have. You can see that I share 53% of my DNA with my sister, but that leaves 47% that we do not share.
Overall, 269 genetic cousins on 23andme have accepted contact with me & my sister. We both share DNA with 77 of them. Then there are 100 relatives that I share DNA with, but she does not. There are also 92 relatives that she shares DNA with, but I do not. If I did not have her tested, I would have missed out on these 92 relatives.
So to summarize, if you don't have parents available to test (mine are deceased), siblings are invaluable because they have DNA from your parents that you don't have.
However, getting your sibling tested will tell you nothing about which side of your family a 23andme cousin comes from. After all, by definition, your sibling shares the same parents (and grandparents, etc etc) that you have.
To try to narrow down which side of your family a 23andme cousin comes from, you have to turn to relatives that you have from only one side of your family.
I have had my two half-sisters, my dad's double cousin, my paternal aunt, my maternal aunt, my maternal uncle, my maternal great-uncle, and my maternal great-aunt tested.
Here is my comparison with my two half-sisters.
The theoretical percentage shared between half-siblings is 25%. You can see that I share more than expected with one sister and less than expected with the other. Again, there's no real rhyme or reason for this, it's just random chance.
Getting my half-sisters tested allowed me to sort out which of my parents many of my relative finder cousins came from. The "con" of testing half-siblings, though, is that they will have many matches that you do not have because you have only one parent in common.
Here is my comparison with my aunts and my uncle.
The theoretical percentage shared between an aunt/uncle and a niece/nephew is also 25%, the same as half-siblings. You can see that I share almost that exact amount with my two aunts, but slightly more with my uncle.
The difference between your half-siblings and your aunts & uncles, in terms of DNA testing, is that you are related to all of the 23andme cousins that your aunts and uncles have. Even if you don't share a DNA connection with them, you are genealogically related because your aunts and uncles don't have any ancestors that you don't have. Your half-siblings do.
So to a greater degree than with my half-siblings, I can identify relatives and make a genealogical connection with someone, even if I personally do not share any DNA with that person.
I have also had my maternal great-uncle as well as my maternal great-aunt tested (my grandmother’s siblings).
The theoretical percentage here is 12.5%. You can see that I share a bit less than expected with each one.
Getting my great-aunt and great-uncle tested has been very useful because it allows me to identify many relatives that come from my maternal grandmother’s side of the family. And what I said before applies to this relationship too --- even if I don’t personally share DNA with all of the 23andme cousins that they have, they are still my relatives because my great-aunt & great-uncle do not have any ancestors that I do not have.
And last but not least, I have tested my dad’s double cousin.
I wrote in a previous post about what a double cousin is, as well as more info about the double cousins in my family. But I will summarize here --- double cousins share all four of their grandparents in common rather than just two. This occurs when two siblings from one family marry two siblings from another family.
My dad would be expected to share 25% with all of his double cousins. As his daughter, I have half of his DNA and therefore I would be expected to share half as much --- 12.5%. You can see that I share a little more than expected with this particular cousin.
Double cousins are pretty rare, especially nowadays, but they are very useful in terms of DNA testing because (as with aunts & uncles) all of their relatives are your relatives because they have no ancestors that you don’t have. He also helps me to identify which parent my 23andme cousins come from.
I hope this was a good summary of the family that I have on 23andme and what I have learned from all of them. If you have any questions about my family or about 23andme in general, please let me know :)