DNA match

[JBee]

Just got a hit to my son's ancestry dna.

It comes as an extremely high 3rd to 4th cousin.

He also matches my half sister as a 3rd cousin again extremely high.

However he doesn't match to my great aunt (who possibly didn't have the same father as my grandmother)'s grandson who matches to son as 4th cousin.

Unfortunately this new match has no tree as he was adopted and lives in the US.

What I am trying to find which generation to look at and see where there might be a connection.

My brain is befuddled so could so with some help please lol.

[marquette]

I have a little chart that says 3rd cousins have common great-great grandparents and 4th cousins great-great-great grandparents, so 4 and 5 generations back. As we generally have 16 gg-gps and 32 ggg-gps thats a lot of family to cover.

With 16 gg-gps you would only have less than 7% of each one's DNA, so it would not be surprising if you had a completely different bit to a 3rd cousin and not have a match. And around 3% from each of your 32 3xg grandparents.

I tried looking at the trees or gedcoms on ancestry and gedmatch - ancestry is better but only goes a few generations. With Gedmatch, all the ancestors of US people seem to have been born in the US, back to the 1600s. That makes no sense to me and too far back to find any links to mine in England. It might be an anomaly of the website - I have found one of my husbands matches by their unusual name and knowing some of the common descendents.

From each parent you get about 50% of your DNA (my daughter has slightly more of her fathers)
From each grandparent 25%
From each great-grandparent (8) 12-13%
From each great-great grandparents (16) 6-7%
From each great-great-great grandparents (32) 3-4%
From each great-great-great-great grandparent (64) 1-2%.

And apparently more than 90% of everyone's DNA is common to every one of us, so we are looking at a very very small amount of DNA.

Di

[JBee]

Thanks Di

I'm not sure of these dna relationships in ancestry as my it gives my half sister's relationship to my son as a lst cousin not aunt???!!!

I've asked my contact to try and find his birth parents names and will try and work back from that. I have an inkling he may be a descendant of two boys that were sent to Canada when their dad (great great uncle) died, one returned the other didn't. There's several people researching that line who would probably help him.

There again it might be a totally different line (probably the Irish line where I have little knowledge.

[kiterunner]

Your half-sister's relationship with your son is the DNA equivalent of 1st cousin because she shares half the amount of DNA with him that she would if she was a full aunt.

[JBee]

Thanks Kate

All this DNA stuff is still a mystery to me.

[Olde Crone]

Am I missing something? If he doesn't know his birth parents' names, how will he know if he's found them?

OC

[JBee]

I've asked him to find out any names from his adoption file but he's on holiday at the moment so might take some time.

[Olde Crone]

JBee

Sounds like you will be doing all the work! Proceed carefully, his birth parents may not wish to be found, especially if that involves quizzing other relatives who may not know of his existence.

OC

[JBee]

Thanks OC - wasn't thinking about that part just the family tree. Will have to advise him of the consequences - if he gets back to me. He isn't a youngster though - mid 50's