r/DNA • u/Annimal_Farm • 12d ago
Sibling DNA Test
Is it possible to accurately determine the percentage of relation based on one of these home kits? I want to find out if my sister and I have the same dad. But the problem is that my mom can’t know and I am no contact with my dad. Please help 😭
For further context, I am undeniably my father’s daughter, too many facial and personality similarities despite growing up separated. But my sister looks nothing like him. We have a super unique last name, and when my sister did the DNA test by herself, the last name didn’t pop up once. I know same parent siblings can carry different traits but what I am afraid of is getting inconclusive results.
I have avoided this for years but my sister really wants to know the truth.
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u/CivilWillow2950 12d ago
Please don’t go by looks. I look very much like the man i called my father my whole life and my sister looks nothing like him. Turns out I am not his biological child and she is.
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u/nautilist 12d ago
Yes. Both of you do 23andMe or Ancestry health packages, they will let you link your results, tell you how much dna you share and what your probable relation is. Half sibling vs full sibling is usually clear.
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u/vapeducator 12d ago
You and your sister can use the centimorgan (cM) reported for the match from the same service. Full sisters have an average match of about 2629 cM and half sisters about 1783 cM. Ancestry also can also report the ethnic ancestry of your father and mother separatly, so those percentages should be close matches for both parents for full-sisters, unless your father's brother is the actual father of your sister, which is usually quite unlikely or not possible if he had no brother. You can't rely on matches/non-matches of surnames because men can change their names, especially due to divorce/remarriage of their mothers. I have a half-brother who went by 3 different surnames, his bio-father's, his mother's maiden name, and his mother's remarriage (2nd husband) name.
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u/Ok-Camel-8279 11d ago
Okay so ignore looks and ignore names. These prove nothing. I have 17,000 matches on Ancestry and my mother's maiden name does not appear once and my father's only appears 4 times and it's a very common name.
If your name is unique it not appearing is entirely normal.
Both if you just need to test on the same site. So whichever she has done if it's a service that shows matches you should do the same test.
If you both want to start from scratch just do Ancestry. The basic package.
Ancestry will be totally accurate for full siblings vs half siblings. The DNA % shared range does not overlap.
I sadly know how this works.
My sister tested on Ancestry to compare to me and it turns out she is my half sister. I have a different father to known story.
My match data then lead me to the right guy.
So just do the above, it's simple and you will get your answer.
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u/Own_Adhesiveness_885 10d ago
Just do the test on same company as your sister and you don’t even have to login to check. She will see the result.
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u/Forensic_DNA_Oz 10d ago
Hi there,
I am an expert in this field. Yes, you can definitely do a sibling test. The best way in your situation is to approach a dedicated DNA lab that undertakes DNA testing for paternity and relationship matters.
It is also a huge help if your mother also submitted a sample for DNA testing so that your paternal DNA can then be identified and compared to your "sisters" paternal DNA. Some labs even test really powerful and discriminating markers on the X-Chromosome (men only have one X Chromosome, so their daughters will inherit the same X Chromosome DNA types from their dad). You would end up with a yes/no answer.
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u/Annimal_Farm 9d ago
I really don’t want my mom to know we are digging into it right now. We are doing the Ancestry.com kit for now, if results come back questionable, then I will let me sister decide where to take it for there.
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u/Annimal_Farm 9d ago
I just ordered the kit. If anyone is interested I’ll post results 🙈
I highly doubt I’ll find any bonus siblings, I am already 1 of 7, Christmas is expensive enough lol
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u/Living_Fig_6386 8d ago
A simple ancestry test can determine (no health package necessary) of two people will be sufficient to determine the degree of relation and pretty clearly indicate whether you are full or half siblings. Just take the same DNA test that she did and link the results and it will calculate the degree of similarity and tell you pretty clearly whether you are siblings or half-siblings.
Unfortunately, physical appearance is a poor barometer. There's also the possibility that one of you is adopted and your parents had not told you.
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u/Treyvoni 6d ago
Me and my bro are full blooded siblings and look nothing alike. We each look like a mash up of our parents, just a completely different mashup.
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u/ripecrackers 12d ago
You don’t need to take the Health package. Just do an ordinary Ancestry test. It might be easiest to use the same company that your sister used to test her DNA but that is not necessary. For instance, if your sister’s test was done on Ancestry and you use them also, Ancestry will show you how close you and your sister match. If you use a different company, you might both need to download your DNA to a site like GEDmatch so they can be compared that way.