I'm so sorry you had to live with such hell at home, Cloudy. I can relate; I was also physically abused, terrorized, and emotionally destroyed by my brother as a child, while our parents stood by and did nothing. He would break down my bedroom door with a butchers knife in his hand during his rages, beat and rape me. I also hate my brother intensely, and he's been the subject of many of my nightmares. There is nothing wrong with admitting that you hate him and want him dead.
But you can't possibly be responsible for your parents situation and safety. They after all did raise him and thus contributed to him being the way he is, while you did not. Personally, I was so relieved once I no longer had to hear him about him at all, once he no longer existed as far as I was concerned, and anyone he may be hurting was well outside of my sphere. You should have been protected from the beginning, you shouldn't even have to hear his name spoken ever again.