Cutting off siblings

My father is a narc and has put me and my siblings against eachother all my life. My middle brother let this get to his head and resents me and my eldest brother and him are super close no matter what my middle brother says or does to me. I have no desire to have my middle brother in my life anymore and it hurts me that my eldest brother doesn’t take my side like I always stick up for him. At this point I’m considering cutting them both off, has anyone done this? Was it the right thing to do?