Have you tried to address your pain over this situation with a counselor? Nothing can be done to undo the past. All you can work with is the now and the future.
I am also an adoptee but wasn’t told, so all my childhood I thought my sister and I were biologically related and related to my parents. My sister developed cancer when I was 11 and died when I was 13. My mom became mentally ill and remained so all my teen years. I found out I was adopted by accident while looking for my birth certificate when I was 18 and and was a few weeks away from getting married.
To say my mom handled my discovery poorly is an understatement. It was discovered when I was 7 months old that I had a severe heart condition. The day I discovered I was adopted she said I should be grateful because a lot of people told her when my parents found out I was sick she should have given me back.

Nice huh? Gee thanks for taking pity on the poor, pitiful, sickly orphan. My mom was feeling threatened and probably afraid of rejection.
My point is your childhood can not be changed. The fact that you have adopted siblings can not be changed. The fact that they have other biological relations can not be changed. The only thing we have control of in our lives is how we deal with life and the things the things that happen that are not in our control. I had some pretty horrendous teenage years -and it took time to work through it. I still love my parents -even though they are imperfect, don’t always get it right and my mom, even though she is better, still has mental break downs.
So first I would suggest asking God to help you forgive your parents failings, and to help dissolve the bitterness and jealousy you feel toward your adopted siblings. Then I would suggest seeking a counselor to help you work through it all. Your feelings, your pain is real -but to keep holding on to it -only harms you further and keeps you from freely living a life that you do have control over.
God bless, you are in my prayers.