Hello this is my first time making a reddit post but I really need some advice and opinions from unbiased people because this whole thing is making me tear my hair out. Also throwaway just so that this can’t be traced back to me. 

So I (18F) recently got into contact with my half brother after almost 15 years of silence and although my mom and my sisters were ecstatic I wasn’t. When my sister texted me saying that my half brother had contacted her saying he wanted to talk to me I just felt dread and anger, this is in part because I still hold a lot of resentment towards him.

 (this part might get rambly but I promise it's important) The reason why I resent him is because of our father. I have some vague memories of my father but some of the few things that I remember was how secretive he would be, he would leave for days at a time with no clear explanation and always saying he was occupied at work. Now obviously you can see where this is going, he was having an affair, or rather my mom was his affair partner and I was his secret kid. Now before you guys get mad at my mom she truly had no idea what my dad was hiding and in fact she didn’t find any of this out until after my dad died, then that's when everything started making sense. Both my mom and I had spent a lot of time with my half brother which is why it hurt so much more when she found out that he knew the whole time. He knew that my dad had a wife waiting for him at home, he knew how much my mom loved my dad and he never said anything and after my dad died it was like my half brother disappeared off the face of the earth. 

Which brings us to now, my mom and sisters are really pushing for me to reconnect with him saying that he is the last thing left of my dad, but honestly? I really couldn’t care. I said that I still hold a lot of resentment towards him but at the same time I don’t feel happy or excited talking to him because to me he is nothing more than a stranger, I don’t know anything about him and he doesn’t know anything about me. And also after 15 years of silence I just sort of accepted that I would never see him again and I was okay with that, I am happy with my life right now. I’m happy with just my mom and my sisters. 

And although I’ve tried to express this to my mom and sisters it’s like they’re choosing to ignore me. My graduation is next month and the topic of who to invite came up and my mom and sisters are really pushing me to invite him but I don’t want him there. 

My mom randomly texted me during school saying that she was going to invite him and I actually felt sick to my stomach at the thought of having to see him again. I quickly texted her back that no, she’s not going to invite him and that if she did I would never forgive her. Then later that day I tried talking to her and expressing to her that I don’t want him here and I thought that I had finally gotten through to her but as soon as we got him she just said “Oh i'm so happy you're going to invite your brother” This made me unbelievably mad that I actually told her if she was seriously ignoring what I had just told her, that what part of he’s not invited did she not understand.

Later that week when my mom, sisters and I were discussing what family members were coming to my graduation we were counting how many people were coming my mom said ‘What about your brother?” This once again made me mad that I actually yelled at her and told her that she needed to get over my brother coming to my graduation because it was never going to happen, my sisters actually backed my mom up and told me that I should reconsider,.

This whole thing is making me want to scream, especially because my mom and sisters are usually super understanding of my feelings but I just don't understand why they would be pushing so hard for this. So tell me reddit AITA?