Only child, resentful of my adopted siblings . . .

Hi. It's 2024 and I am doing research for my MA dissertation in Creative Nonfiction (telling true stories, well). I am a bio kid. I lost my brother to SIDS - traumatic! My parents decided to heal from the trauma by renovating a house and starting the adoption process. Within a year or two of losing my bro (in the 80's - so no child therapy or ANYTHING), I had two 'new brothers'. They were half-brothers to each other and one was older than myself - supplanted as firstborn. I am 42 and have finally refused to play happy families. I have had to break contact with my big brother - he's a narcissist! My life was full of eating disorders and suicidal depression - for about 15+ years and no one helped me until I finally found an amazing rehab and I now have a nuclear family of my own and 2 gorgeous children. As a bio kid, I have always felt alone, overlooked, rejected and abandoned by my bio mum! The irony. I am bitter and resentful but I am seeing a therapist - for my healing. And.... I want to write a memoir about my experience as a bio kid.