If you don't share DNA with a cousin are you not related?

[Intevel]

Can someone explain how you are related to a cousin if you don't share a strand of DNA? Yes your parent might share a strand...

But for ALL INTENTS AND PURPOSES, other than being in the family tree, aren't they basically almost the same as an inlaw or a spouse?

The ONLY thing that makes you related to someone is if you share DNA, right?

[DRNewcomb]

......The ONLY thing that makes you related to someone is if you share DNA, right?

"Genealogy" vs "Family History" can of worms.

[Germanica]

Can someone explain how you are related to a cousin if you don't share a strand of DNA? Yes your parent might share a strand...

But for ALL INTENTS AND PURPOSES, other than being in the family tree, aren't they basically almost the same as an inlaw or a spouse?

The ONLY thing that makes you related to someone is if you share DNA, right?

No. Biological relation isn't the sole definition of relation.

[Intevel]

I didn't seem to get an answer.

[ltd-jean-pull]

I have a 4th cousin that I share no DNA with, nor with his sister. His uncle shares DNA with one of my parents, but he doesn't share any DNA with my parent. He matches several other cousins, so he undoubtedly is descended from the same ancestors.

Initially I thought it was a shame we didn't share more than very small slithers, but now I think it'd great that we didn't get the same parts of the DNA pie that our mutual gtgtgt-grandparents were dishing out. It's actually been beneficial for trying to take the tree back beyond these gtgtgt-grandparents.

However, if his uncle hadn't tested I may not have found him.

We're still fourth cousins though.

[T E Peterman]

1st cousins share about 12.5% of their autosomal DNA.
2nd cousins share about 3.125% of their autosomal DNA
3rd cousins share about 0.78125% of their autosomal DNA.

Spot the pattern? For each additional degree, divide the percentage by 4.

I say "about" because this is an average. It can vary upward or downward and, with each additional degree, the variation becomes greater.

People match over 90% of their 3rd cousins, but only about half of their 4th cousins & maybe 10% of their 5th cousins.

Because the average number of cousins goes up about ten-fold with each degree (ie, 3,000 3rd cousins; 30,000 4th cousins; 300,000 5th cousins), most matches reported in Family Finder will be among the tiny minority of 5th or more distant cousins.

Timothy Peterman

[Germanica]

I didn't seem to get an answer.

I answered you. You asked "The ONLY thing that makes you related to someone is if you share DNA, right?" and my answer was no, DNA is not the sole definition of relation.

If what you're asking is "If you don't share any DNA segments with a cousin, are you really biologically related to them?" then you worded your question poorly.

Technically, we all share DNA. If you lower the min thresholds for matching far enough, you will pretty much match everyone. So technically, you do share segments even with distance cousins you don't "match". But once the amounts are below a certain threshold there's no way of knowing whether the segment is shared from a recent common ancestor or whether it's by random chance, which is why companies use min thresholds to filter matches out and you don't always match more distant cousins.

So there does reach a point where some cousins share the same amount of DNA segments with you as someone who is not related to you. I suppose you could say that cousin is no longer biologically related to you, but it doesn't not mean that cousin isn't related to you at all.

[Intevel]

I answered you. You asked "The ONLY thing that makes you related to someone is if you share DNA, right?" and my answer was no, DNA is not the sole definition of relation.

If what you're asking is "If you don't share any DNA segments with a cousin, are you really biologically related to them?" then you worded your question poorly.

Technically, we all share DNA. If you lower the min thresholds for matching far enough, you will pretty much match everyone. So technically, you do share segments even with distance cousins you don't "match". But once the amounts are below a certain threshold there's no way of knowing whether the segment is shared from a recent common ancestor or whether it's by random chance, which is why companies use min thresholds to filter matches out and you don't always match more distant cousins.

So there does reach a point where some cousins share the same amount of DNA segments with you as someone who is not related to you. I suppose you could say that cousin is no longer biologically related to you, but it doesn't not mean that cousin isn't related to you at all.

Right so basically if the cousin is not biologically related to you, then he's basically like an adopted relative? You're only related through marriage then, not through science and blood?

[dna]

@Intevel

Is one's spouse (a wife or a husband) one's family?


Mr. W.

[Cats]

Right so basically if the cousin is not biologically related to you, then he's basically like an adopted relative? You're only related through marriage then, not through science and blood?

If that is the case please tread lightly with the information. However, I believe that relationships and relations transcend DNA.

[MoberlyDrake]

Are you saying you have a first cousin who is supposed to share biological grandparents with you, but who shares no DNA with you? If so, you have a non-paternal event somewhere. One of you, or one of your parents, in the shared line is not the biological child of one or both of his/her supposed parents. This could be a very messy situation to deal with and you might want to test more family members before you say anything.

On the other hand, if you know someone who you know is not related to you, and you call the person "cousin" because he/she is "just like family", you would, of course, share no DNA. This could happen for instance, if your uncle married a woman who already had a child from a previous marriage. Some children are in the habit of calling very close friends of their parents "aunt" or "uncle". Biological family and social family are two different things. There is the possibility that you could happen to share DNA with someone you do not think belongs to your biological family because you share distant ancestors you know nothing of. If you share a whole lot of DNA with someone you do not think you are related to, it's due to an NPE.

[dna]

Are you saying you have a first cousin who is supposed to share biological grandparents with you, but who shares no DNA with you? If so, you have a non-paternal event somewhere. One of you, or one of your parents, in the shared line is not the biological child of one or both of his/her supposed parents. This could be a very messy situation to deal with and you might want to test more family members before you say anything.

On the other hand, if you know someone who you know is not related to you, and you call the person "cousin" because he/she is "just like family", you would, of course, share no DNA. This could happen for instance, if your uncle married a woman who already had a child from a previous marriage. Some children are in the habit of calling very close friends of their parents "aunt" or "uncle". Biological family and social family are two different things. There is the possibility that you could happen to share DNA with someone you do not think belongs to your biological family because you share distant ancestors you know nothing of. If you share a whole lot of DNA with someone you do not think you are related to, it's due to an NPE.

NPE or infants were (mostly mistakenly) switched at the hospital.

Posted on 2018-04-02.

Mr. W.

[Germanica]

Right so basically if the cousin is not biologically related to you, then he's basically like an adopted relative? You're only related through marriage then, not through science and blood?

No, you're not related by adoption or marriage, because neither of you were adopted or married into the family. You're related by ancestry. You can share ancestors with someone but not share enough DNA to show up as a match, because again, DNA is not the sole definition of relation.