whats up with in common

[Cats]

I have a cousin who tested with FTDNA as did me, my mother and brother.

My mother has 62 in common matches with her.
My brother has 53 in common matches with her.
I only have 11 in common matches with her.

Isn't that a bit strange?

[dna]

No, it is not strange at all.

If your cousin can share her screen with you, you two should take a look in your cousin chromosome browser at your DNA, your brother DNA and your mother DNA. It should be easy to spot that you share with her different parts of autosomal DNA, than your brother and your mother.


Mr. W

P.S.
Please let us know.

[Jim Barrett]

I have a cousin who tested with FTDNA as did me, my mother and brother.

My mother has 62 in common matches with her.
My brother has 53 in common matches with her.
I only have 11 in common matches with her.

Isn't that a bit strange?

I think it is a bit strange that your brother has almost 5 times the number of "in common with" matches with your cousin as you have.

Of course you and your brother have a different mixes of your mother's DNA and your brother must have more of your mother's DNA that matches the DNA of your cousin. Since your mother has the most in common with matches with your cousin I assume the cousin is from your mother's side of the family.

If you have access to the myFTDNA websites for your mother and your brother look at the "Shared Centimorgans" and the "Longest Block" for each of you and your cousin. Your mother should have the highest values for both values and your brother probably has the next highest values and you probably have the lowest set of values.

[Cats]

I manage all the kits.

me: 1st Cousin - 3rd Cousin 285(shared) 35(longest) X-Match

brother: 1st Cousin - 2nd Cousin 412(shared) 60(longest)

mother: 1st Cousin, Aunt/ Niece 750(shared) 117(longest) X-Match

So funny that we really have so many in common matches.

[Cats]

In common not working properly.

I just looked at how many in common relatives my brother has with me and my mother. Results have to be incorrect.

My brother has 707 in common relatives with me
My brother has 12 in common relatives with my mother

I have 709 in common relatives with my brother
I have 92 with my mother.

Anyone else getting strange results with the in common feature?

[LSS]

It should say my brother has 120 (not 12) in common with our mother.

[Frederator]

I just looked at how many in common relatives my brother has with me and my mother. Results have to be incorrect.

My brother has 707 in common relatives with me
My brother has 12 in common relatives with my mother

I have 709 in common relatives with my brother
I have 92 with my mother.

Anyone else getting strange results with the in common feature?

It looks weird on the surface, but if your mother is from what might be considered an 'underrepresented' ethnic or other social group, at least compared to your father, that might not be as weird as you'd think.

I just did a survey of the largest segments for every paternal match my brother and I could confidently attribute to a specific ancestor. Results show that 50% of the cM are attributed to one great grandparent, 23% to the other great grandparent, and the remaining 27% to our grandmother. Each from different ethnic groups. Very different rates of representation within the database.

[Cats]

You are absolutely correct about the under represented ethnic group. My mother is Lithuanian. Such a difference in the numbers. Thanks for your response.

[dna]

You are absolutely correct about the under represented ethnic group. My mother is Lithuanian. Such a difference in the numbers. Thanks for your response.

It bothers me that your results are not symmetrical: 707 and 709...

Mr. W

P.S.
Different numbers of matches to your cousin that you, your mother and your brother have is not related to underrepresented or over-represented populations.

[Frederator]

It bothers me that your results are not symmetrical: 707 and 709...

Mr. W

P.S.
Different numbers of matches to your cousin that you, your mother and your brother have is not related to underrepresented or over-represented populations.

You're going to keep yourself awake at night over a discrepancy of 2? Those are either typos or reflect a trivial difference in application of the in-common filters.

[dna]

You're going to keep yourself awake at night over a discrepancy of 2? Those are either typos or reflect a trivial difference in application of the in-common filters.

No, but if it were in my family, I would look again, since I am always operating under an assumption that when looking at Adam results in common with Eve, I am seeing the same set of matches as looking at Eve results in common with Adam.

I am fully aware that it could have been a typo, or more FF matches showed up between two queries, or some testers changed their matching preferences between two queries. I have possibly missed some other valid reasons...

I would not loose any sleep over it, but it turned out that Adam has one ICW match less than Eve does. So I downloaded filtered matches for both Adam and Eve, got rid of anything beyond the 4th column, sorted and compared. Hmm, Adam is missing his 3rd-5th cousin (36cM, 14cM for Eve). He is missing that match both from ICW and from the unfiltered list. I will retest tomorrow, and bug FTDNA for an explanation if the discrepancy persist after 7 days, since counting shared cMs in Eve's Chromosome Browser confirms that it appears to be an omission for no reason (it adds up to around 25cM, 14cM for Adam).


Mr. W


P.S.
The above is for a sibling pair from my family. I did not use their real names though. I have also looked at the other sibling pairs from my family and they were fine.

[LSS]

It isn't a typo and I checked and rechecked as well. Not sure why the difference of the 2 matches between me and my brother.

Still perplexed by the difference of in common matches with my cousin.

[MMaddi]

It isn't a typo and I checked and rechecked as well. Not sure why the difference of the 2 matches between me and my brother.

Still perplexed by the difference of in common matches with my cousin.

Do you realize that, on average, 1st cousins share 12.5% of DNA that came from their common grandparents? This means that roughly 87.5% of your DNA is different than your cousin's DNA.

This is one factor for what you're seeing as a lack of common matches with your cousin that your brother has. Based on random recombination, your brother has received from your grandparents more of the same segments that your cousin has than you received.