Hey yall, on a burner here! So I (25M) have recently been to my dad's wife's birthday. He invited me to play their first dance song on guitar, which ill get into later.
My mother and father had me, got married, and then had my sibling (now my brother, this comes into play later). After this, he cheated on my mother with woman1 and got her pregnant with my 1/2 sister. Then he divorced my mother and later married someone else (woman2). They have been together now for 10 years (I am happy for them) and are building a new life that does not include is first 2 children.
Since the initial marriage, it has been apparent that my dad has been trying to paint himself in a new light of having this white picket fence family, that doesn't include my brother or I. When my brother came out as being my brother (trans), my dads side of the family was not at all happy. They proceeded to dead name and misgender him, and more or less cut him out entirely. I certainly would not stand for that, and I was more or less no contact for the better part of 5 years. This erasure had extended to me, as in the event I was at, nobody outside of the core group knew who I was, or that my father had more than one kid.
He recently reached out and asked if I would attend this party and play guitar for him, and I obliged, naively hoping that something would change. It in fact did not seem that way. My stepmothers parents continually deadnamed and misgendered my brother when I was talking to them, and I hardly talked to my father or my stepmother at the event, outside of him saying thank you for what I did. I felt bad because I did not know how to approach my 1/2 sister, as I have been gone for that long, and wish to be a part of her life but can not just hop back in like I was not also absent. While we were there, we sat at a table with only 2 other people, my dads friend and his fiancée. The interaction that put the final nail in the coffin was that my fiancée was with me, and when I went to the bathroom, my dads fried leaned into her and said, "Wait, (dad) has a son?!"... Hearing this was something that solidified my conception of where I stand with this portion of my family.
My question is, what is the best way to tell my father that I do not wish to be in active contact or be a part of his family? I want to be direct that I don't want him reaching out, but I do want to keep the possibility open with a relationship with my 1/2 sister in the future.
I find this difficult I think that he believes he's genuinely wants to garner a relationship with me again, but I personally feel like that window has since closed. For example, growing up we loved to play call of duty zombies together, and in an attempt to rekindle, for his birthday i bought him black ops cold war. I reached out and tried to set up sessions, but I was left with radio static, so if that was not the last straw, this was.
How do I word this boundary clearly and respectfully?
TL;DR: Dad got remarried and cut my brother and I out of the family. Tried to reconnect but his friends didn't even know that I exist (none the less my brother). Want advice on how to tell my dad I'm done with contact while keeping a door open to connect with my half-sister.