So once again we have a viewer question that I wanted to take a look at.
And I've made other videos on this,
but this one was nice because I could draw out something really well for it.
And it is about multiple relationships when you're related to somebody in more than one way.
Do you share more DNA from these multiple relationships?
So, let's go to their question: Both my first cousins are married.
They are also first cousins to each other. Interestingly, from a historical standpoint,
it's actually estimated that the majority of marriages from history were this type of marriage-
you know, two first cousins or maybe second cousins.
While it may be unusual, nowadays, from a historical standpoint,
which means from a genealogical standpoint, that's the way most of the marriages are.
And so, that's why this is an important question.
Does that mean I share more DNA with my first cousin once removed- their children?
I like to draw things out because it helps us visualize it.
And so, I have it drawn out here.
You can see that there's three cousins here all related to the same set of grandparents.
And, they happen to have each of their parents are
siblings- two of these cousins married and they have children.
So, that is what we have here.
So, the question then is really this relationship between the viewer and their cousin's children.
So, how much DNA do they share?
What is their relationship?
How do we go about doing this?
And drawing is a great way to do this. Whenever we're looking at relationships,
really, we can draw a line to see - how they're related.
- who their most recent common ancestor is or ancestral couple is
- and that would give us an idea of how much DNA they should share.
So, let's do this.
We're going to draw a line. First off through, obviously,
her mom or this person's mom- his mom. And it goes up to the grandparents.
So, we have an ancestral couple.
Now, we're going to start and go down through their daughter.
This would be the viewer's aunt. In this case,
to their cousin. And then, to their cousin's child.
So, this would be a first cousin once removed and that's one path of relationship.
But we can also see that there is another path of relationship.
Now, it goes the same way initially. It goes up to the grandparents,
except this time it goes down through the uncle of the viewer,
to the cousin of the viewer, to the first cousin once removed.
So, we have two lines of relationship here. And each one of them is a first
cousin once removed. And so, in this case,
they would be double first cousins once removed. This couple here.
They are not double first cousins. They are first cousins who happen to marry.
And so, this is where trying to keep these relationships separate can get a little confusing.
In this case, we have two lines of relationship
between our viewer and their first cousin once removed.
And they both happen to be first cousin once removed.
So, they are double first cousin once removed,
which means they would share the same amount of DNA as a double first cousin once removed.
Now, how much DNA is that?
Well, that's actually the same amount of DNA as a first cousin.
So, this first cousin once removed to them
shares the same amount of DNA on average as each one of their first cousins.
Which is pretty cool, when you're thinking about it.
You share as much DNA with this you know first cousin once removed of yours as your parents do.
And it's just because they happen to have gotten their DNA through both sides
that is linked back up to this person.
I'm looking at this. And I'm also going to say.
I believe they would have some small segments of- no!
I take that back. No, they wouldn't
have any fully matched [segments] because this person only received
their DNA through their mother to the most recent common ancestor.
So, they would only match on one set of their chromosomes.
This person got parts of both sets of their chromosomes from the same common ancestor.
So, they would just actually match more. And what you would probably see is you
would probably see more smaller segments than the first cousins had up here that make up that DNA.
So, whenever you come across a potential multiple relationship,
I always suggest drawing it out to see if you have that correct.
Now, this one was rather simple because they were just double first cousins once removed.
I have, you know, some in my family tree that are like a second cousin
once removed and a third cousin, you know, through different lines.
So, those of you who have you know even more complicated ones or maybe three or four lines of
relationship for it make sure you draw that out so you can understand.
Okay, how exactly are these related?
And who are the most recent common ancestors that I need to be concerned with for this?
So, the answer to your question is- yes! That first cousin once
removed is going to share more DNA than what they typically would.
In fact, they're going to share about as much DNA as each one of their parents do with you.
Now, if you want to learn something more about DNA then check out this video up here.
And be sure to like this video and subscribe to our channel.