2nd cousin -- or perhaps not?

[HughC]

My strongest match is 395 cM with a 2nd cousin.  Unexpectedly high but not impossible.
There are several other 2nd cousins with matches in the range 264 to 200 or so.

Far down the list comes one with only 45 cM.  Even if his grandfather was in fact only a half-brother of my grandfather, that seems rather low.  Is it possible, or what could be going on here?  He has shared matches with several cousins on that side of the family, but I can't tell how strong because my Ancestry subscription has lapsed.

[David Nicoll]

DNA painter gives 45cM, a 1 in 200 probability of being 2 cousin, so low but possible.

[Spelk]

Hugh, Why do you think this person is second cousin? Is that what the paper trail is indicating or is that a guess by Ancestry?

[HughC]

He is a grandson of my grandfather's youngest brother.  I was wondering whether that brother was not a son of my great-grandmother, but they all continued living together as one apparently happy family.

Another possibility is that the sample of saliva was from one of his children, but submitted under his name.

[Glen in Tinsel Kni]

He is a grandson of my grandfather's youngest brother.  I was wondering whether that brother was not a son of my great-grandmother, but they all continued living together as one apparently happy family.

Another possibility is that the sample of saliva was from one of his children, but submitted under his name.

Someone registering a kit as their own when it isn't happens more often than we may realise (I have a group containing questionable kit registrations, often a pink icon named John or a blue icon named Susan for example). Unless there is a sufficient quantity of close or definitive matches to indicate a wrongly assigned kit or half relationship it is often a waiting game.

[Josephine]

Shortly after I did my DNA test, I convinced one of my brothers to do it as well, and it has been really interesting to see the differences in percentages of our shared DNA matches. (I manage my brother's results; he has no real interest in any of it.)

First example: I have a known cousin. Her grandmother was my great-grandmother's sister. This cousin is my father's 1st cousin 1x removed; I think this makes us 2nd cousins 1x removed (please correct me if that's wrong).

My brother shares 130 cM with her, whereas I share 50 cM with her.

Second example: A cousin who was unknown to us until recently. He was a DNA mystery but I think I've cracked the code. If I'm right, this man's mother was my grandmother's half-sister. This would make him my father's 1/2 1st cousin and my 1/2 1st cousin 1x removed (or 2nd cousin -- again, I'm not sure).

My brother shares 306 cM with him, and I share 221 cM with him.

All this to say that some of these DNA results can vary quite a bit and, unless we have DNA from the people in question who are more closely related, I think sometimes we're still going to be left with our best guesses.

[HughC]

Thank you, Josephine.

The way genes are passed down is evidently even more random than I thought.

[Josephine]

You're welcome, HughC.

Yes, this is why it can be helpful to have a full sibling do the test as well. I paid for my brother's test, mailed it in, and did all the online stuff, which meant that all my brother had to do was spit into the tube and give it back to me in its box.

I've just looked up a known 2nd cousin in a different branch of my family. His grandmother was my grandmother's sister. My brother shares 234 cM with him, and I share 172 cM with him. Ancestry estimates that my brother is this man's 2nd cousin but that I am this man's 2nd cousin 1x removed or 1/2 2nd cousin. In reality, I'm his 2nd cousin.

Even though I've seen posts by people who say they have easily solved the mystery of their great-grandfather's unknown bio dad, or their mystery 3x-g-grandmother, etc., this hasn't been the case for me.

I recently opted to spend the money on a subscription to Ancestry, plus the additional subscription required to use their "Pro Tools," and it has been worth it for me in this one mystery DNA case because it has enabled me to compare the results of various DNA matches between me and my brother.

The DNA mystery cousin in question doesn't have a tree on Ancestry or anywhere else, which made it a lot more difficult to figure out the relationship. Being able to see the matches that this cousin and I have in common, and the matches that this cousin and my brother have in common, and then to do that with all of those various matches, has helped to solidify my case. In the end, though, it seems that it will still come down to my best guess.

(It would help if this man would see and respond to the messages I've sent him via Ancestry and Facebook, and then if his mother or her sister would do the DNA test, but I'm not holding my breath. He hasn't been on Ancestry in over a year and I don't know if he ever checks his PMs on Facebook.)