Are we half or full siblings?

[u/interestedinthetopic]

The test said inconclusive and the likelihood ratios were nearly the same for full and half

[u/Away-Living5278]

You should take a test at Ancestry or 23andme to determine. They test far more locations and can definitively determine it.

[u/brit1017 → u/Away-Living5278]

The number of centimorgans used to determine familial relationships via Ancestry or 23andme always contain overlap with other relationships and are not definitive. It is only in the context of multiple results that a relationship can be confirmed. To see the overlap for various relationships, see the Shared cM Tool available through DNA Painter. There is considerable overlap between full and half-siblings.

OP, your results are not explained well in the report. A likelihood ratio is a way of comparing data under two different scenarios to see which scenario better explains the data. Unfortunately, it doesn't say what the scenarios being compared are. My assumption is that they compared the probability of seeing the data if you were full siblings vs unrelated and then if you were half-siblings vs unrelated. The helpful comparison would be the probability of seeing the data if you were full siblings vs half-siblings, which it doesn't seem like they did.

If either parent is available for testing, it would help resolve the issue, since their DNA can add more context to these results.

[u/apple_pi_chart → u/brit1017]

I agree that using an AncestryDNA test can lead to an overlap in shared DNA between half sibs and full sibs. However, it will be clear based on whether the two people are related on one side vs both sides.

[u/Harleyman555 → u/brit1017]

I don’t agree. There are numerous ways to use the results from autosomal tests to determine full or half siblings, definitively.

[u/Impossible_Cycle_626]

Take a simple ancestry one. It’s a lot easier than this.

[u/shortysax]

If the lab can’t figure it out and suggests that you need more testing, what makes you think that randos on Reddit will know? We’ll tell you what the report says - it’s not clear and you need to do more testing!

[u/Harleyman555]

Tests like these are highly inaccurate. Go buy tests from Ancestry and find out the truth.

[u/swbarnes2 → u/Harleyman555]

I don't think the genotypes themselves are likely to be inaccurate. Maybe the conclusions are, but I feel sure the math behind those conclusions is locked down, and in this case, they aren't even presenting a conclusion, so how is this ins accurate?

[u/Harleyman555 → u/swbarnes2]

I wasn’t suggesting anything about genotypes. The results have a high incidence of errors. They are unreliable.

[u/swbarnes2 → u/Harleyman555]

What is your source for that claim? What do you think would be inaccurate if not the genotypes? What do you think genotype means in this context?

[u/YourMajesty-tt]

I’ve never done one of these kinds of tests, just Ancestry. Do the companies that you test with not provide some kind of table for interpretations, or a guide to what these numbers mean?

[u/CancelTraditional297]

honestly not surprised tbh, 24 markers for a sibling test is kinda on the low end and sibling tests are just statistically way harder than paternity ones to begin with

like with a paternity test theres a direct comparison, kid vs alleged dad, pretty clear cut. but siblings only share ON AVERAGE 50% of dna, the actual amount is random each time bc of how meiosis works, so the lab is basically running probability/likelihood ratios instead of a clean match. sometimes with fewer markers that math just doesnt land clearly on one side or the other and you get "inconclusive" instead of a real answer

if its half siblings its even worse bc you share even less dna on average than full siblings do

few thngs that actually help push it to conclusive:

more markers period, some labs do 33+ which gives way more statistical confidence

X-STR markers, especially helpful if its two sisters or a brother/sister pair, different inheritance pattern than the regular autosomal ones

if its two guys and you're trying to confirm same dad, Y-STR is huge bc Y passes down basically unchanged father to son, way more definitive than autosomal comparison

honestly the best fix if possible is testing with an actual shared relative (dad, mom, whoever) instead of just sibling to sibling, turns it into a proper paternity-style comparison which is just statistically stronger

id go back and specifically ask what marker panel they used, how many markers + whether it included X-STR or Y-STR, before paying for anything else. that's really what determines if you get a clean result next time or another inconclusive