How come third cousins are not listed on Ancestry?

+3 votes
279 views

I am new to DNA. I have about a hundred unknown 4th to 6th cousins listed on Ancestry. However, I did not match with 3 third-cousins I personally know who took the test with Ancestry. One of them used Gedmatch and she told me there’s very little between her and me. All those third-cousins are related to me through a paternal great great grandfather (Ulysse Paultre in my tree). Is that common to inherit so little from an ancestor that close? In the meantime, I ordered a new test from Family Tree DNA just to confirm. Thanks for your help.

WikiTree profile: Ulysse Paultre
in Genealogy Help by Living Angus G2G3 (3.4k points)
retagged by Ellen Smith

5 Answers

+14 votes
 
Best answer

There is a 10% chance of not matching a 3rd cousin who is biologically related to you, This % increases the more distantly you are related

see https://www.familytreedna.com/learn/autosomal-ancestry/universal-dna-matching/probability-relative-share-enough-dna-family-finder-detect/

If there are lots of known 3rd cousins who tested and you don't match any of them, then I would start to suspect a mis-attributed parentage somewhere.

by Michelle Wilkes G2G6 Pilot (168k points)
selected by Living Angus
Thanks Michele. I think the new test will answer the question.
Note that my niece matches with those 3 cousins. Being the daughter of my sibling, I guess it could be a mistake in the test and not a mis-attributed parentage. Or maybe I just took very little from that great grand parent.
+2 votes
Several of my cousins that come up as 4th to 6th cousin matches on my DNA once I figure out how they’re connected to me some of them are about third cousin range. You just have to follow the trail see how closely they were related to see if it’s actually that distant or not.
by Charlotte Shockey G2G6 Pilot (979k points)
+2 votes

AncestryDNA confidence level is different than the others.  According to AncestryDNA for 3rd Cousins.

"it’s interesting to note that (at this degree of separation) we are accurately able to predict about 98% of the possible relatives that are out there—in other "words there is a 2% chance that our DNA analysis can NOT recognize an actual relative of yours."

It's important to note that none of the DNA services tell us how accurate the prediction is, only how many they will detect.

If you go your cousins Ancesty.com profile, it may show you as an AncestryDNA cousin were you can view the match.

 

by Ken Sargent G2G6 Mach 6 (61.6k points)
+6 votes

Harry, that new test is probably not going to be much help.  It might help a little, as my new Family Finder kit *is* finding more matches than my Ancestry kit.  But the big problem is we don't receive even proportions of the DNA from our ancestors.  I got a Family Finder kit for my sister late last year, and I cannot believe how many more people on my mother's side she matches than I do.  I found my first connections to others through my Bullard line, but when I compare with *any* of them, I get nothing, zilch.  I was beginning to think there was a mistake in one of our trees.  Then I tried my sister's kit, and she matches great, with all of them!  Both small and larger segments, essentially proving our relation after all.  I now know that there are a number of lineages where she got all the DNA and I have none!

So what I want to recommend is not test yourself, but find a full sibling and get them tested.  If they test as a full sibling to you, then anyone that matches them is a match to you, even if you can't get your own DNA to match them.  After awhile, you may be able to tell which of your kits, yours or your siblings, will test the best against various lineages.  And if you get a third sibling, you may find additional matching capability you don't have either.  Each sibling and parent test gives you more tools to try.

by Rob Jacobson G2G6 Pilot (136k points)
edited by Rob Jacobson
Just to echo Rob's comments, I've tried it both ways. I tested me with ancestry and ftDNA - obvious difference in the matches within the companies as they have different databases, but put them both on gedmatch and you'd be hard pressed to find the difference.

If you put the two files together onto Promethease then one of the things it does is tell you if there are any differences (for me that was 2 SNPs out of 404 thousand - not a bad error rate between the two companies).

I got a lot more mileage out of testing my two brothers, and I'm now eagerly awaiting my sister's results - getting a test kit out to her in Jo'berg took 3 months though. I think they sent it by camel.
+2 votes
It all depends on what parts of the ancestor "salad" you get. That is why I gift DNA kits to lots of relatives...25 so far!!! Some get better matches than others, but they all unravel secrets to our origins!!! Oh, I like my FTDNA test better than Ancestry which was my first and didn't give me everything I was looking for. I use FTDNA for my gifted kits...
by Debbie Parsons G2G6 Pilot (150k points)

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