My adoptive father died and no one notified me

This is the short version so I hope this makes sense. I always thought I was adopted but my family lied to me. At almost 28, married, with a toddler and pregnant with twins I find out the truth by ordering a pre-adoption birth record after years of my motherӔ saying I wasnt adopted. My birth mother turns out to be severely disabled and the sister of my adoptive mother. My birth mother was institutionalized and raped by a serial rapist/pedophile when she was 18 and I am the product of that rape. I am bi-racial, the rest of my family is Caucasian. My adoptive father had a degenerative brain disorder that appeared to be genetic so a big part of me wanting to know the truth was to know for sure that I was not related to him. So when I find out IҒm adopted my adoptive mother (technically now my aunt) is furious and tells me my birth mother is dead and that she doesnt know anything and that my whole family is mad at me for digging. I tell her that to have a mother/daughter relationship there needs to be honesty and it needs to be okay for me to talk about being adopted and my birth mother who is alive. We mutually cut contact off after that. She makes it clear I need to pretend I wasnҒt adopted and never bring it up again, and I make it clear that there needs to be honesty. A few months later when my twins are now 3 months old I swallow my pride and take them to see my sister (adoptive parents bio child that is 8 years younger than me) and adoptive mother. That was two years ago and not once has my ғmother tried to contact me. Well tonight I found out my father died. The last time I saw him was 4 or 5 years ago, he was in a wheelchair and already had severe enough dementia that he didnԒt know who I was. I did not find out the truth until after he was mentally losing it so I do not have anger at him and honestly I do believe all of this was more of my motherӒs choice than his. He was an abusive alcoholic during my childhood, and I live 300 miles away from him so these are contributing factors to me not being active in his life. However, he had been sick for a few months, and they had known a few days before he died that the time was approaching, he was 52 so I always had thought there would be more time for me to figure this out. My mother told my sister not to contact me and made no effort herself to contact me. My sister called my work the day before his service, a full week after he was dead and left a message that she knew was getting put in my box and did not tell them the message was urgent. I believe my mother intentionally did this to get back at me for wanting to know the truth, wtf, my birth mother has the mental capabilities of a 1 year old and my bio father is incarcerated for raping a little girl, my birth parents are not happy shinny people that were going to replace my adoptive parents yet my mother made me choose, truth and bio mom, or lie and my ԓreal family. I really think she intentionally had my sister call last minute so that she could tell everyone at his funeral that I didnԒt care enough to show up. I knew my mother was cold, but to not tell me my father was dying is just cold. She is remarried so it wasnt even like he was her husband any more. Right now I am so angry at her for denying me to see my dad again out of spite that I canҒt even begin to grieve. I just hope no one else has someone as cold for a motherӔ, thanks for listening.