I understand the feeling. My birth was not planned or wanted I don't think. My grandmother told me many times growing up that me being born almost killed my mother. I also got beaten and verbally trashed at home, so others took notice and provided me with fake "love". Fake was better then nothing. I don't know the answer to your question as to why anyone can be cruel to any child. I have repaired my relationship with my family in many ways, but to this day they do not know about the predators, or that by the time I was 8 five of them had gotten to me. I am working with a T now who will help me decide about telling my family.
I do know this: I am not, was not, and will not ever again be defined by what everyone told me while I was growing up. My T says I need to work on anger now, and Im down for that as I don't know how to do it, but she does. I know from my own progress that working with a T is critical. Because of my T, I seen now that abuse is not who I am, it is something I went through and the depth of my past only indicates the height of my future. We can win!
“We can easily forgive a child who is afraid of the dark. The real tragedy of life is when men are afraid of the light.” - Plato