My Mother told me I was a "mistake and never wanted " when I was growing up. My older brother and sister were idolised.

That is sad and very wrong for your mother. It's a cruel thing to say to a child, let alone treat them differently. I agree with Blossoming that talking with a professional about it all might be good for you.

That is so sad, what an awful thing to do to a child. Would some form of talking therapy help you make sense of it and maybe come to terms with it? It doesn’t sound as if your siblings had a happy time either, in their own ways .