DNA is a record of relationships. So, you may be
wondering what kinds of relationships can actually find
from DNA and in fact, we actually had a viewer that
asked us this specific question. Can Ancestry DNA find
siblings or half siblings? Well, DNA can tell us who are
siblings or half siblings are but this is more specific. This
has to do with the Ancestry DNA test. When you take that, is it
going to identify these siblings and half siblings? I
can start by pulling up my wife's match list and you can
see the very first match she has happens to be her full
siblings and that is her brother. They share roughly
2300 centimorgans and so without doing anything else,
Ancestry identified her brother as her full siblings. So, the
first part of the question is answered, can Ancestry find
full siblings? Yes. Ancestry is going to find full siblings.
Now, you may be wondering, well, how do they do that and
that is somewhat interesting question. So, let's talk about
full siblings and half siblings here. This is a part of a table
from Leah Larkin's website that talks about how much DNA
siblings and half siblings might share. Now, you may be
wondering, I don't see siblings or half siblings anywhere.
Group A in DNA and and what the DNA detective put together is a
group that includes siblings and really it's the only people
in the group is siblings and group B is a group that
includes half siblings. I'll talk about that here just in a
second. So think of group A when you see it as siblings and
group B right now as half siblings. We could see that
from three different sources. DNA detectives. AncestryDNA and
the Shared CM Project that they have different values.
AncestryDNA and the Shared CM Project those values are very
similar and DNA detectives is somewhat although they go to a
higher amount that they have little asterisk there and that
asterisk is important because they point out that DNA
detectors uses 23 and me data and 23 and me double counts the
fully identical region full siblings share about 800
centimorgans that is fully identical so if you take 3900
centimorgans subtract 800. you get 3100 centimorgans, which is
roughly about what ancestor DNA and the shared CM project have
but in essence when looking at siblings with group A and half
siblings group B what we can see is that there is either
very little or just a small amount of overlap in that 2100
to 2300 range. most of the range of what you would expect
for either siblings or half siblings does not overlap. Now
the reason why Ancestry can identify full siblings right
off the bat is simply because in this range 2100 to 3100
centimorgans other than that small little overlap on the
short end there's no other relationship that shares that
amount of DNA and so Ancestry can confidently say that this
person is Devin's brother because they share 2300 plus
centimorgans now when I'm talking about group B we are
talking not just about half siblings but also aunts uncles
nieces and nephews double first cousins and grandparents
grandchildren all of these people share that same range of
DNA and this is from the DNA detectives chart so if we go
over to one of Devin's aunts and we look we see that their
first matches are not siblings even though they do have a
siblings it just says close family in fact here's close
family to a first cousin eighteenhundred 79 centimorgans
is shared now in this case eighteen00 is too small to be a
full siblings. So, it falls into this group B category.
Ancestry just classifies this in the close family range which
includes half siblings, aunts, uncles, nieces and nephews,
double first cousins, and grandparents, grandchildren.
Now, you can go in yourself and you can actually identify this
as a half siblings in which case then that will show as a
half siblings but Ancestry by itself just from that test is
not going to identify a half siblings so what are the
differences between full siblings and half siblings when
we start to go down and look at it on the chromosomes well here
is an example of those first couple that were siblings my
wife and her brother you could see that they share and this is
all from 23 and me they share 2400 centimorgans which are
half identical. 52 segments and 736 centimorgans which are
completely identical in 25 segments. Now, visually, the
lighter purple is the half and the darker purple is the fully
identical. One of the things that you'll notice is that the
fully identical always happens within this half identical
unless you're really at the ends of the chromosomes but
half siblings They only share one parent. So they don't
actually have any fully identical DNA. They only have
half identical DNA. So this is my wife's two aunts that are
half siblings. They share roughly 2000 centimorgans on 23
and me. 47 segments. Now the interesting thing here is if we
look at the number of segments it's roughly the same because
they are siblings. All of those fully identical segments are
contained within anyone of the half identical segments. So it
really doesn't add any new number of segments. So, this is
one of the things that I'm actually thinking about doing
some more research on is seeing from half siblings and full
siblings, how many segments they share and seeing whether
or not that actually is just a overlap of really the same
number of overall segments on average or if there's a little
bit of a difference between roughly from all the the
examples that I've seen from my known family. It looks like it
is roughly about the same between whether it's half
siblings or full siblings. The difference being full siblings
all have some segments within those half segments that are
fully identical. So, we can answer that question about
Ancestry DNA. Yes, Ancestry DNA is going to identify full
siblings because the DNA signature of full siblings is
unique. No other relationship has that in that they share
between about 2303, 000 centimorgans and they have
these fully identical regions within their DNA and Ancestry
will not identify half siblings as half siblings. They will put
them in close family because there's some other
relationships that they could be. However, you may be able to
eliminate those relationships based on the information that
you know and you can then label that as a half siblings. Half
siblings share about 1, 300 to 2100, 2200 centimorgans which
for the most part is less than what full siblings share and
they have any fully identical regions. Now, if you would like
to see a video about the differences in relationships
and how that looks on DNA, you can watch this video up here
but if you'd like to learn something more about DNA, then
watch this video down below. Be sure to smash that like button
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