Ah I know exactly what you mean. I myself am adopted; although I do know my biological mother kept none of us but for a far more darker reason, which I won't go into just yet. But anyways, I sometimes have troubles with my adoptive parents as well like you. I have been threatened to be dis-owned before.

What I am trying to say is that they raised you. They can never replace you. You're their son. They picked you.