My family is also like that. They are fast talkers and interrupt constantly. They don’t mean anything by it, it’s just how our family is. Nevertheless, it used to really trigger me. Learning to acknowledge but disregard the emotional responses situations like that impose gives me the mental space to focus on what I’m saying, not how I’m saying it. And when I focus on what I’m saying, I’m forced to speak more slowly and deliberately because it takes time to translate your thoughts into coherent sentences. Good luck!