Do you want to narrow down your matches so you know how they
might be related to you? Well, today, we're going to show you
the tool that can help you get started doing that.
Howdy, I'm Andy Lee with Family History Fanatics and this is a
segment of DNA. Be sure to subscribe to our channel and
click on the bell if you want to be notified about
upcoming episodes. Now, as genealogist, one of the things
we're trying to do is see how people are related to us or
related to other people. With DNA, we can actually see how
people might be related to us as far as which families are
common ancestors without even knowing anything about that
other person's family tree. In order to do this, we need to
have some matches that we already know how they're
related. So, for instance, if have close family members like
first cousins or second cousins that you know which
grandparents or great grandparents you're related
through then you can start to classify your matches into
groups of people that are related to certain of your
ancestors. To do this we're going to use a tool on GEDMatch
Genesis. Now down in the DNA applications there's a tool
called people who match both of one or two kits. So what you
need is you need two kit numbers. This would be yourself
and one other known relative. And for today, I'm going to use
my cousin that I know we're related on my dad's side. So,
when we get there, you just have to enter in the two kit
numbers. Next, it's going to ask you about the threshold you
want to use and I'm not going to change those basic
thresholds initially. I can display the results. Now, what
Genesis has done is it has gone through and it is compared my
match list with my cousin's match list and put information
together. This first part is going to be the people that we
both match and so you can see in this first set columns is
going to be the information about me, how much shared DNA,
what the largest is, and in the next set of columns is going to
be the amount for my cousin and this is going to be different
numbers. So, for instance, I know here that this is my dad
and you can see that I match him at 3500 centimorgans and my
cousin matches him at about 1800 centimorgans because he
would be my cousin's uncle. Now, this page actually has
three different lists. This first list is going to be the
one that we both match and since I know how we're related
through my paternal grandparents, all of these
people are also going to be related in that way. So, I
don't need to be looking at my family tree on my mother's side
because I know that they're all related on my father's side. If
you scroll a little bit down the page, you're going to come
to the next section and that is going to be the people that
only match me. They don't match my cousin. Now one of the
mistakes that people make here is that they think that okay
well if the ones that match both of us have to be from my
father's side then these ones must be from my mother's side.
But that's not the case. A lot of them are going to be from my
mother's side but not all of them. Some of them are still
going to be my from my father's side. It's just that I match
DNA with them and my cousin doesn't match DNA with them. As
we scroll down further the page we get to the next list. This
is the third list on here and these are the matches for just
my cousins. So, I don't match him but he matches him and
again, this doesn't mean that these people have to be related
through his dad in this case. They may be related through his
mom through that same common ancestor. The difference is is
I just don't share DNA with them. Now, remember, once you
get out to third cousins, you don't share DNA with all of
those cousins. You only share with about 90% of your third
cousins. So by fourth cousins it's forty-five percent and by
fifth cousins it's down to fifteen percent. So there may
be a lot of these people on this list that I'm still
related to. I just don't share DNA with. Now one way that this
tool is really useful. Particularly for people who
don't have tier one access is if you have one of your parents
then you can basically phase the matches on your DNA. So I'm
going to change this from my cousin now to my mom. Now,
whereas before with my cousin, I was focused really on the
matches both kits because all of those I know come through my
father. With this, when I'm comparing it to my mom, that's
actually not the list that I want to focus on. Now, all of
these people are related through my mom which is great
but there's also going to be a lot of matches that my mom has
that I don't have that are also related through my mom. So, I
need to look at those two lists but if I scroll down the list
of matches that match me but they don't match my mom these
are now going to be the matches that have to be through my
father because I got half of my mom's DNA and so every single
one of my matches that's going to be on my mother's side
I have to match with my mom but any matches that I have that my
mom doesn't have have to be from my dad's side and so in
that case this is the list that is going to be the most
important particularly if I don't have my dad's DNA because
now, what I've been able to do is I've been able to take my
mom's DNA and figure out which of those matches of mine are
from my dad's side. So, after you have started to sort your
matches based off of other known relatives and it's time
to start playing with those thresholds a little bit and see
what other information you can pick up. Now, there's two
thresholds to worry about. First is the threshold of the
largest segment and this is how big of a segment does somebody
have to have a order to call a match so they may share a lot
of DNA with you but if it's all in really small segments they
may not show up as a match so in this case usually I just
leave this one at 10 although sometimes I will cut it down to
you know about seven or so if you just have a lot of matches
because of your family then maybe you want to increase this
number a little bit but the one that I use more often is this
next one and this is the threshold of total matching
segments so we look at of the segments that you match with
and how much CM do you have to have in order to call this a
match. So for instance, I may have a largest segment at ten
but maybe I just want to look at matches that share at least
thirty centimorgans with me. Now, this is really important
with families that have endogamy because you have so
much shared DNA and a lot of that may be in just these
little segments. The higher your total matching segment is,
it's going to eliminate out some of those max who may be
just very very distantly related to you. So I've done my
search and now what you can see is that this match list is a
whole lot shorter than what it was in the beginning. At the
beginning there was about 150 to 200 people on that. Now
there's about 20 and half of them are my immediate family
that I already know. So if I just wanted to look at the ones
that me and my cousin are most closely related to then this
would be the list that I am looking at. By the last thing
is the generation difference. Now if you have a endogamic
population and you may want to use this. For instance it's set
at ninety-nine and that's just the default which is going to
make sure that it encompasses everything. So if you are let's
say two generations removed from somebody and one of your
matches is and the match you're comparing it to is four
generations removed from that person. There's a difference of
two generations. By chain this number, you're going to be able
to eliminate some of those matches and in endogamous
populations that may be useful. For most people, I haven't
actually found that this is very useful in helping to
narrow down your matches. But give it a try and just see what
numbers help work in figuring out how some of those matches
relate to that second kit that you're comparing to. So the
comparison of two kits is a great way to help narrow down
your matches and start to classify people into different
family groups. So if you have any relatives that are already
tested, you our kits combined with yours to see how your
other matches might be related to you. If you have any
questions about how to use this tool, put it in the comments
below and if you like this video, give it a thumbs up and
be sure to share it with all your friends.