Half second cousin link

[brave eric]

After 40 years trying to confirm my great grandfather I have traced a very likely HALF SECOND COUSIN. Ie we appear to share one great grandfather.

On my side the link is my father’s father’s mother “X”

On my half second cousin’s side the link is her father’s mother’s father “Y”

X and Y are half brother and sister

I am ignorant of DNA techniques and would appreciate advice on the likelihood of the reliability of results from us testing

Thanks

[Flemming]

Hello Eric, and welcome to RootsChat. Can you confirm which site(s) you've tested with and is it just yourself or have other family members tested?

It would also help to know the centimorgans (cMs) shared with your likely half second cousin. For your own info, the link below takes you to a shared cM calculator on DNA Painter which shows the likely relationships for ranges of cMs.

https://dnapainter.com/tools/sharedcmv4

Are you thinking that the father of your father's father's mother and the father of your possible half 2C's father's mother's father are the same man?

[brave eric]

Thankyou for our response, unfortunately I have made errors in presenting this and it should read

After 40 years trying to confirm my great grandfather I have traced a very likely HALF SECOND COUSIN. Ie we appear to share one great grandfather.

On my side the link is my father’s father “X”

On my half second cousin’s side the link is her father’s mother “Y”

X and Y are half brother and sister ie share the same father

we have not invested in testing yet as we wanted to find out how feasible this is .
I have tried to alter my original post but so far without success

[Flemming]

Hello Eric, if your possible half 2nd cousin were to test, you’d be looking at shared DNA of around 120 centimorgans (cM for short).

This would be quite a high level of cM to share with someone and would certainly indicate that you’re on the right track in terms of the closeness of connection. As an example, I have ten matches on Ancestry who are above 100cM and all are third cousins or closer.

Even if your possible half 2nd cousin doesn’t test, and you don’t have any matches above 100cM, you can still piece together connections with people who share lower levels of DNA and show (for example) that you’re directly related to the ancestors of X and Y’s father.

If you do test, just a personal view, but I’d go with Ancestry, partly because their DNA database is the biggest, and also because their algorithm is one of the most robust (some might say too robust!). You can also upload Ancestry DNA tests to other websites such as MyHeritage and FTDNA - although you can’t upload other DNA tests to Ancestry. The upload to MyHeritage and FTDNA is free but you have to pay to unlock their analysis tools (which Ancestry doesn’t have at all, and so something of a downside with this site). Then there are totally free sites (like GEDmatch) that you also might want to try.

For what it’s worth, I’d do the test. I spent years not finding my grandparents using just paper methods but tracked them down within a few weeks after getting the DNA results. And RootsChatters will always be happy to help you, either on the forum or through private message if matters get sensitive.

Good luck!

[Flemming]

Hello again, something else that might help: on Ancestry, you can create your family tree, enter your suspected great grandfather, and the system will search through your matches' trees (if they have one) and other associated trees to see if you and your matches share any ancestors of your 'suspect'.

This is called 'common ancestors' (because the system shows the common ancestors you share with a particular match). I've got over 100 of these, with most of them proven correct by paper research.

You have to link your tree to your DNA test kit, but you can keep it private if you don't want others to see what you're doing. We can help with that as well.

[brave eric]

Brilliant. thank you that is so helpful