Related through my mom or my dad? (blood, surnames, father)

[JrzDefector]

So I did 23andMe and then uploaded my results on GEDmatch. I got an email from a guy who seems to be a second or third cousin. Is there any way to tell if we're related through my mother or my biological father? (Bio dad was literally a sperm donor, so we know NOTHING about him, or at least next to nothing.)

The family history he gives indicates that his family came over at least a couple hundred years ago, but as far as I know, my mother's family only arrived in this country about 100 years ago. That makes me suspect that we're related through my bio dad. The really funny part is that one of the last names he gives as being in his family background is my non-bio dad's last name. It would be funny if Pop and I were actually relatives by blood.

[PA2UK]

Originally Posted by JrzDefector

So I did 23andMe and then uploaded my results on GEDmatch. I got an email from a guy who seems to be a second or third cousin. Is there any way to tell if we're related through my mother or my biological father? (Bio dad was literally a sperm donor, so we know NOTHING about him, or at least next to nothing.)

Without testing your mother (or bio father), it's not really possible to tell whether the person is a match on your mother or father's side.

The exception is if you are male, and you share X-DNA, then you share an ancestry on your mother's side. But the absence of shared X-DNA does not necessarily mean the match is on your father's side. If you are female, then shared X-DNA can be from either side. Since the match is male, if you share X-DNA then that at least narrows it down to HIS maternal side (though that's assuming it's not possible you share ancestry on both sides, which is actually more common than you might think).

These charts show X-DNA inheritance for males and females...

Male:


Female:

The family history he gives indicates that his family came over at least a couple hundred years ago, but as far as I know, my mother's family only arrived in this country about 100 years ago. That makes me suspect that we're related through my bio dad. The really funny part is that one of the last names he gives as being in his family background is my non-bio dad's last name. It would be funny if Pop and I were actually relatives by blood.

That's not impossible, but shared surnames doesn't necessarily mean you are related by that surname. Unless it's an extremely rare name, it's more likely to be just a coincidence.

[JrzDefector]

Originally Posted by PA2UK

Without testing your mother (or bio father), it's not really possible to tell whether the person is a match on your mother or father's side.

The exception is if you are male, and you share X-DNA, then you share an ancestry on your mother's side. But the absence of shared X-DNA does not necessarily mean the match is on your father's side. If you are female, then shared X-DNA can be from either side. Since the match is male, if you share X-DNA then that at least narrows it down to HIS maternal side (though that's assuming it's not possible you share ancestry on both sides, which is actually more common than you might think).

These charts show X-DNA inheritance for males and females...

Male:


Female:




That's not impossible, but shared surnames doesn't necessarily mean you are related by that surname. Unless it's an extremely rare name, it's more likely to be just a coincidence.

Thank you - this was hugely helpful. GEDmatch is really hard for me to decipher.

[brownbagg]

but does 23 and me seperate each side by x and y. the only way i could think of, is you actually had a y test done.