Can DNA prove my relation to deceased grandparent?

Factual Questions
1

I recently reached out to a genealogy company to explain that in order to apply for a special dual citizenship, I am trying to prove that I am the grandson of my deceased grandfather. He died long ago and his body is not available for testing. My grandmother his also deceased.

A salesperson from the genealogy company suggested it is possible to prove my relationship with my grandfather through DNA testing of presumably myself and various family members (cousins? aunts and uncles?)

Is this definitively true? How many people would need to be tested to prove I am my deceased grandfather’s grandson?

2

You can’t prove it definitively, even with a sample from your grandfather himself. But you can certainly increase (or decrease) your confidence in your assertion that he’s your grandfather. And you can also increase your confidence that, even if you’re not descended from him, you’re descended from someone else of the same nationality, which might be enough for your purposes.

One difficulty, of course, is that even if you can prove that certain people are your aunts, uncles, and cousins, you would then have to prove that the old man is in fact their grandfather. And whatever evidence you would have for that, why don’t you have it for yourself?

Is he your father’s father or mother’s father? If your father’s father, and if (as your name implies) you’re male, you could use Y chromosome testing to prove that you’re of the same family line (as it’s traditionally been defined in most cultures, patrilineally). You could instead be descended from his brother, or a male-line cousin, or so on, but as mentioned before, those might be enough.

3

Normally that sort of family relationship is proven with documents for citizenship purposes. Are the relevant documents unavailable for some reason?

4

I’d be surprised if the naturalization bureaucracy of any country is sophisticated enough to be using DNA evidence to determine eligibility. They generally like old scraps of paper to prove relationship.

5

I agree; the only opinion that matters is that of the government in question. What proof do they say they need?

6

I follow some groups on the topic of genetic genealogy. If you try using this type of testing for legal purposes you are going most likely going to have to break new legal ground and unless you have a lawyer working with you and the cooperation of the government agencies involved you might as well not try.

7

OP: What country’s citizenship are you trying to add?

8

Genealogy websites dig up documents too. Map your family tree and you’ll be surprised at what they can offer.

Census records indicate where family lived. There’s registration cards for the WWII draft. Wedding Certificates, Death Certificates. I found all of these for my mom and my dad’s family.

One interesting example, I always thought of my paternal grandfather as a farmer. But he filled out his WWII registration as a carpenter. That was work he did when his farm didn’t require all his time.

9

He might have figured that the Armed Forces didn’t have any particular need for farmers, but that they could use trained carpenters. And he might have been hoping for that as an MOS, rather than cannon-fodder infantry.

10

That could be it. I see how it’s better to go into the military with a useful skill. My granddad never got called up. My dad’s oldest brother and his 1st cousin were in the Navy and fought in the Pacific.

The OP’s best chance is to put together as many family documents as possible. His connections to that family should appear in some of those documents.

11

Carpenter was an official specialty rating in the Navy until after WWII - but farmer probably wasn’t Carpenter's mate - Wikipedia (my father was a Naval carpenter’s mate during WWII). Also I suspect that all farmers know a certain amount of carpentry.

12

Probably, yes, but as mentioned above that might not be good enough for some bureaucrat someplace.

Example: Uncle Bill is alive, and has a birth certificate listing Grandpa Jim as his father. Your Dad is long dead, and his birth certificate is irretrievable. DNA should be able to show that you and Uncle Bill have an avuncular relationship, therefore Grandpa Jim is your grandpa.

Most relationship tests won’t be able to distinguish a half-sib and an uncle. Perhaps Grandpa Jim and Mom had a kid, Uncle Bill, who is not in fact related to your dad at all. In that case Grandpa Jim is not your grandfather. If Mom is around, and not related to Uncle Bill at all, then your relationship to Uncle Bill has to be through your Dad. It may be possible based on age to prove Dad cannot be Uncle Bill’s father (if Uncle Bill is older than Dad, for example).

People are working on genetic techniques to be able to distinguish half-sib and and avuncular relationships, but the research is on going, and probably shouldn’t be taken as “proof” just yet.

13

Austrian citizenship.

14

I guess, too, that depends on what they are testing.

So antique citizenship laws required paternity descent - if your father was a citizen, you are. (IIRC, wasn’t this the case with UK citizenship too?) If so, then what you need is to prove who is your father’s father. So does 23-and-Me or Ancestry, etc. do Y-chromosome testing? And can you identify other male relatives -Paternal uncle or his son, grandson, etc.?

I do recall reading that while these genealogy sites do tell you who is related, it is not the same tests as a forensic DNA. However, you could do these tests to establish that it is worth the expense of doing a forensic test - if this is what the authorities need. (and assuming there’s no “pedigree errors” (the polite term) for anyone involved. To be certain, it would help to test multiple family members, especially if you have two paternal uncles and they have sons.

DNA-101: You have 46 chromosomes, 23 pairs, one of each pair from each parent (hence, 23-and-Me). you get a random 23 from each parent, either from their father or mother. For a male, you got the Y from your father’s 23rd pair, which is XY; if female, and X from Dad and one from mom’s XX pair.).

So statistically, you should have roughly 12 of your 46 (25%) are the same chromosomes as your grandfather. (and same from grandma) Meanwhile, your uncle or aunt will have another random mix, from each pair they may get the same your parent got or the other - so 2 siblings will have a 50% match, statistically (half of those from father, and half from mother, so 25% from father). Two half-siblings, 25%. For the next generation - cousins - again, each gets randomly one of each pair of each parents’ chromosomes, and in each case 50-50 if it’s the same as the cousin got. So two full cousins should match 25%, half from grandfather (12.5%) and half from grandmother.

So theoretically statistics say there should be about 6 of your 46 chromosomes should match your full cousin, give or take. hence, test multiple relatives. If you are both male, both from sons of grandpa, the Y will definitely match. Of course, that Y doesn’t prove much by itself since even if you are both male line descendants from the same great-great grandpa it will match. Hence the same test, multiple relatives, will give a statistical likelihood of relational distance. If the only pair of ancestors going back quite a ways that you have in common are grandma and grandpa and you share about 12% genetic material, it’s a safe bet.

And after all that, sometimes the chromosomes will split up and crosslink during cell division, creating a fractional match.

In the end, birth certificates and marriage licenses are usually the way to go. If you can find relatives, especially still in the old country, they probably have an idea where grandpa and mom or dad were born.

15

I think you have your answer. The DNA test could probably reveal that the man in question is a grandparent. That that would be more than acceptable when you are building a family tree.

But the proof you need to provide a government in an effort to prove that you should be granted citizenship is likely much more substantial.

16

So presumably this is about citizenship for descendants of Austrian citizens who left due to Nazi persecution. You need to talk to experts on that particular process, and it is very likely it doesn’t currently include any provisions for people who have close cousins who have the right documentation to qualify through showing a relationship to those through DNA. In that case you’ll need a lawyer who knows how to get through bureaucracy with evidence outside of the ordinary.