Any genetic scientists around to help me understand the results of a sibling DNA test?

[SnotsGotTheBoobies]

My sister and I always grew up thinking we had the same dad. But a few weeks ago, my mums current boyfriend said my sister wasn’t my full sister. He quickly back tracked, but I couldn’t stop thinking about it, so I ordered a sibling DNA test to see if we are full sisters or half sisters.
The test they did came back as inconclusive, so they looked for more markers. That also came back as inconclusive.
They sent their findings in an email. I have been up all night trying to figure out how it all works and what it means, and I think:
for each row of DNA, mine has to match my sisters for us to have that DNA in common. There are 53 rows, and my sister and I share 14 pieces of DNA. 14 is 26% of 53, so we only share 26% of DNA?
I obviously may have this completely wrong. But if somebody can help me with what percentage of DNA my sister and I share, I’d be really grateful, as if my workings are right, then it looks like we are only half sisters doesn’t it? As we share closer to 25% than 50% DNA.

Anyone suggesting that the Dad here should be roped into genetic testing on some kind of pretext when the test could reveal that he isn’t the genetic father (and when that’s the sole purpose of testing), is being very unethical. Whatever you want to do, do it upfront, OP.

When you do an ancestry test, you will see a lot of DNA matches. Filter them in order of relationship, not recently tested. It will place your closest matches at the top of the list and potential relationships. If you and sis both do one, then click on her name, or she on yours, and choose matches in common. Any shared dna relatives will appear. Look for the ones you both share to begin. You know of a possible father, so do a surname search as well. He may not have tested himself, but if his blood kin did, they will pop up. I prefer ancestry. Also, the DNA Detective group is fantastic. Best of luck in your quest!

There are a bunch of tutorials on YouTube that show visually how to figure out where your dna matches place in your tree.

@Christmasiscominghohoho just to tell you that you can see a name on one of the photos.

thanks. I reported for it to be removed.

shouldn't of done it when I was so tired!

There’s an example of this in my family. Three siblings. Not mine. Two with strong genetic similarities to an Eastern European father. The third with none, (skin tone, build, baldness, just nothing) and a rumour that there was significant unhappiness in the marriage at the time of conception and delivery and a few more unsubstantiated comments from family friends at the time suggesting he may not be your full brother etc.

So what do we do? Both parents now passed, with zero inclination in the sibling that this is even a potential thing. He grew up with this man thinking he was his father and vice versa.

What’s the point in rocking his world now to say he wasn’t your father and someone who is also likely dead was?

So we will leave it unsolved.

Do not deceive your father into the reasons for doing this. Either be upfront or find another way.

I think it is really off that people are suggesting to ask your Dad to test without telling him why. Totally get that you want answers.

At this point I think you and your sister testing with Ancestry and you can also upload to My Heritage and this will give you a good idea of the answer but bear in mind that if you are half siblings one of you is going to have matches to other families and depending on who has tested it might get awkward so I would do the tests under a random name or initials to give some anonymity.

You results of 25/26 % would suggest you are half siblings.

23andme put the full sibling range as 38%-61%
The half sibling range is 17%-34%
There appears to be no crossover in those ranges.

customercare.23andme.com/hc/en-us/articles/212170668-Average-percent-DNA-shared-between-relatives

Did you get your answer @SnotsGotTheBoobies x