2nd Cousin DNA Accuracy

[Lemki927]

Hi Folks

Wondering if someone can help answer a question. My brother recently did the Ancestry DNA test - in the reference of online relatives, they matched him with a 2nd cousin, who we know. This woman is a cousin on our maternal grandfather’s side - our mother’s first cousin. Ancestry says we are 1st or 2nd cousins, confidence extremely high. So all checks out.

My question is: there was a story floating around years ago that our maternal grandfather was not in fact our grandfather, and the man in question was his first cousin on his mother’s side. Would this Ancestry linkup then invalidate that idea? If that story were true, this woman would technically be our 3rd cousin.

As the DNA is close between the two men who could be our grandfathers, is this test accurate enough to rule out that possibility? I will do the test also in the coming months and see what results come from it.

Any thoughts would be appreciated

Lemki

[Gadget]

Hi and welcome to Rootschat

What is   the centimorgan reading of the match? 

If you click on the info sign under the cousin range, it will give you a cM reading  and the number of segment shared, as shown in the clips below.

You can compare the reading with this chart, which will give you an estimate

https://dnapainter.com/tools/sharedcmv4


Gadget

[Lemki927]

Thank you very much

Ancestry says she is 439 cm and 26

Looks like we are very strong second cousins?

[Lemki927]

We just found another cousin on my mothers fraternal side who registers 366 over 22. 

[Gadget]

Have you done the shared matches test to see if there are any more?

Added - From the chart, you're in the  1st cousin to 1st cousin 2 removed and 2nd cousin range

[Gadget]

It might be worth uploading both test results to gedmatch. That site gives more detailed info on chromosome matching, etc.

https://www.gedmatch.com

You'll need to download the test results and then upload to gedmatch.

[Lemki927]

Thank you

We found more links with people on that side we have known to be third cousins, children of different cousins on that side - all listed by ancestry as 3rd cousins.  It is a large family so there seem to be a few people from each household registered.

I would think this is a pretty good answer to my question, however will try Gedmatch