Use ancestry DNA to determine if my dad is my dad

[User415373]

I have reason to believe that my dad isn't my dad. We're not close, him and my mum split up when I was small and he's been a pretty shit father ever since. So it might just be wishful thinking.
My mum has form for cheating. She's also a narcissist and would flip if I even brought this up.
I look extremely like my half-brother who was born 4 years before me. His father and my mother split up, she got with my dad and I was born. So an overlap is possible.
I have a younger full sister and we're wondering if ancestry or similar might prove the point either way of we all get tested. So it might say my brother is a full sibling and my sister a half or vice versa?
There are companies that offer sibling testing but they seem pretty expensive compared to ancestry which might be able to do the same thing?

If ancestry is like 23andMe (which I presume it is) then you can definitely tell half sibling or full sibling. There’s no overlap, it just tells you. Me and my siblings got 23andme kits for £60 something a few years back.

Sibling testing is a more reliable method. But Ancestry or 23andMe will give you your maternal and paternal heritage. If it doesn't match up with what it's supposed to be, you can assume either a) your parents are wrong or lying about their own heritage or b) they're not your parents.

It doesn't give you a precise match the same way a more expensive test would. You need two samples to test to find a proper DNA match which is what the more expensive ones do. However, 23andMe was enough for me to know if my dad was genuinely my dad or not though.

And now I know I don't have BRCA either!

If you want a better test, often TV companies, science places and similar want volunteers to do DNA tests to find their fathers/test for breast cancer etc and they'll pay for them for the feature. Might be worth keeping your eyes peeled for something like that.

The thing is though, if your test comes back with "half sibling" it still doesn't mean all's as it seems. You could have a completely different dad to the guy on your BC or to your sibling! So in that way it could be inconclusive.

In addition to what others have said..it will also link you to relatives so even if it says half sibling you can figure it all out from the connections

Thanks all. If it comes back half both ways I'll just have to cross that bridge when it comes to it! At the moment I just want to know whether my dad is my dad or not but am obviously unable to involve him.

You can just do your own test. Your siblings don’t need to test (unless they want to). I have no personal connections at all with my dad’s side of the family (as in don’t speak to them) and an Ancestry test showed very clearly that my dad was my dad because of connections to cousins/aunts/uncles.

It is only as good as what family members have also registered. Dn only matched a distant cousin as that was the nearest available.

@mindutopia but my dad won't be testing so won't I need someone else?

My DH did this to check that his parents were really his parents. He confirmed it as, while his parents haven't taken a test, he got a match with a couple of aunts or cousins on either side. So that told him what he wanted to know.

@DontTouchMyDog @mindutopia that makes sense now sorry I was too tired this morning! I doubt anyone on his side has but worth a go! I also don't know his dad and that whole side so that might be interesting.