"I just found out that my half-sibling is my full biological sibling and I don't know how to move on."

I think I need to provide context on this one. Hello my (25f) parents divorced when I was 3. They just didn't think they loved each other anymore and started dating dating other people. my mom my mom got married after 2 years when I was 5 and gave birth to my half brother 2 years after that.

My father married when I was 11 but they didn't have any kids. I live with my mom on work days and live on weekends with my dad. I have a very good and healthy relationship with both parents and my brother.

I wanted to do those 23 and me tests since the only thing I know about my ancestry is that my dad is Russian. I was talking to my now 18 year old brother and asked him if he wanted to do it with me and he said yeah so I sent two samples to the lab and the results came yesterday and I opened them and as the title says we are full biological siblings.

I can't be my step father's child because my ancestry obviously indicates that I am half east European (Russian) and other parts of Europe which my step father clearly isn't and my half sibling's (well now full sibling I guess 💀) ancestry is similar to my ancestry. So that could only mean that my brother is my dad's son?

I really don't see the similarity between him and my dad but maybe it's because my brother is a twin of my mom. So my mom cheated on my step father with my dad after saying that they didn't love each other anymore?! What? But i don't want to jump into conclusions and I will ask my mom about this today when I get out of work so wish me luck.

Commenters weighed in to offer advice and insight:

Fine-Beautiful5863 said:

I would get a test for you and your father first. DNA tests will show that siblings are related, but their level of relatedness can vary.

LakeGlen4287 said:

You have to go talk to your mom.

Ok_Routine9099 said:

NTA. Before talking to your mom, maybe see if your dad will take one - if you have a good relationship with him. Telling him that you took one and had some weird results and you’d appreciate him doing one too. (Don’t tell him about your brother)

ladyyymafia said:

You're processing a lot of new information. If your 23andMe results show that you and your brother are full siblings, it suggests that your biological father is indeed your father, not your stepfather. It’s a good idea to talk to your mom directly to understand the situation. Approach the conversation calmly and openly to get the clarity you need.

And CoconutGirlByTheSea added:

Or, and more likely, her mother cheated on OP’s step father with her ex husband (OP’s bio dad).

The next day, OP shared this update:

I wanted to say that I really appreciate your support and I would like to answer some questions before I continue. Yes my father is my biological dad not just because he is Russian but because we have taken a DNA test for another thing (not because my dad thought I wasn't his so get it out of your head) and he is actually the best dad ever.

No mom didn't cheat on my dad in their relationship. My step father is very Italian with the accent and everything both me and my brother don't have a speck of Italian in the results. his mother would come from Italy and visit us. No there is no "third shooter." Now let's go to the actual update.

Me and my mom have this tradition we spend the evening together like a girls night every once in 2 months I asked her if we could do it tonight (it's 2 am currently so it was technically yesterday) and she said yes. I got to her home and we did what we usually do. Bake something, eat the baked something while watching a movie of my choice and talk about things while wearing a weird facial mask.

I decided that since the mood is so cool why not ask her the question. I was like "hey mom you know about those 23 and me tests right?" She didn't so I started giving a speech about the test. after explaining it I told her I did it with Jordan (my brother) and it came out weird.

She asked what I meant by "weird" I told her that the test said that we are fully related to one another and I kinda laughed but she stayed quiet. "It was wrong right?" I asked her. She got angry at me and asked why I did the test with my brother without asking her first. That's when the realization hit me I got defensive and asked her if she was serious. She apologized and just sat there for a minute or two.

She told me that it was a one time mistake. So basically 19 years ago I was in My dad's home napping mom came to take me but I was sleeping and dad told her that she could cone later and take me or stay and pack my things before I left to her home. She stayed and they ended up doing the dirty? I guess? (Don't let anyone tell you that sleeping doesn't save lives cause it created my brother's lol).

I was pissed at mom and dad and asked her how she could do that. She said that it was an accident and they have never done it after that day and she didn't even know that my brother was my dad's until now. I was angry at both of them they don't understand how much of a problem this could create.

My brother LITERALLY had a fat crush on my cousin from my dad's side (well now OUR dad I guess) but it faded away Jesus christ I even helped him flirt with her! Shit I don't even know what to say I am still too shocked and disgusted. Jordan literally spent years learning Italian just to speak to his grandma. I think I need a proper DNA test without my brother knowing to get some kind of closure.

Edit: I have called my boss and said that I can't come tomorrow. I have also called my dad and asked if we could meet so both of my parents talk and so I could convince him to give a sample for the DNA test