DNA test: 17% likely relationship?

Question

My crazy relative is trying to prove she is the illegitimate child of my paternal uncle (as well as my maternal half-sister). She talked an equally nutty relative (my uncle's legitimate daughter) into doing DNA test. The result was (according to them) that there is a 17% likelihood of their being related. Everyone involved is of the same ethnicity and national origin.

Am I right in understanding that this result is essentially "random"?

Please -- I am looking for a serious scientific answer. This is not a joke, and the accusation is very hurtful to my uncle's widow, who is over 80.

Thanks to those of you who are answering seriously. The relationship is this: The two people who claim they were tested clearly have different mothers. They are trying to say they have the same father.

Kim, thank you so much for that site!

Dan: No, they are not related, although both are related to me. My half-sister and I have the same mother. My cousin and I are children of brothers. The two should have no relatives in common. And yes, they both need counseling, but neither of them would agree.

Answer 1

"The sibling testing is designed to establish either full sibling or half sibling relationship between two individuals. You collect the DNA when and where you want using our home collection swab kit. Our laboratory processes your submitted sample. Results are easy to understand, showing a < 20% ( exclusion ) or >80 ( inclusion ) probability of relationship between two individuals."

Answer 2

17% isnt much but is something, technically speaking the daughter is only 50% his blood 50% the mother. If you relative is claiming that she has the same parents, mother and father as the woman she took the dna test with than it would have been very high %. If shes claiming just her dad is her dad also then it should still be around the 80% ratio. To hush everything up your uncle should just take the dna test seeing as your all related obviously that 17% is because they are indeed related just not immediate family.

Answer 3

At this point the kid is 17 so that means less then a year to go till your husband is no longer responsible for him. So being as there is a good chance that the kid is his then i'd have to wonder why it would even really matters? I mean your husband can easily decide to have absolutely nothing to do with the kid, and in a few more months won't have to pay child support. Don't you think just dropping it and letting it go would be the best idea?

Answer 4

hmm I would say the results means she is a relative, but not the child of the people involved. In order to be a child of, the percentage would be more in the 70 or higher range. It only means there is a 17% likelyhood they are related. This would not be like the child of, sibling of, or anything that close.

Answer 5

Well, they are related aren't they? So they should have some DNA the same.

If they shared a common parent, I would guess that they would have more matching DNA than 17%

Sounds like your nutty relative and the one going along with her should both get some counseling.

Answer 6

If she takes these results to court, they will not stand up as proof she is your uncle's child. Basically, her results prove her less likely to be a direct descendent.

Answer 7

with only 17% chance,that is avery slim chance of being his child. It would have to be up in the 90% to be a reliable testing.

Answer 8

I would think if they had the same father, their genetic similarity would be much higher than 17%. This website had detailed discussion of this, but I didn't see any analysis that spoke to your question.

Good luck,
Dana

Answer 9

are you sure YOU are not the one who is nutty?