thicker than blood

I am who I am because I want to be, and no one can tell me differently. Not my mother, not my sister, not that she could, and definitely not you. You don't know me- you may kiss me you may love me but you do not know me, not at all. I let you in my heart and it's clear that all you want is my blood. I should've known from the beginning.
What's that, it's not true?
Then prove me wrong.