They may kill her....

I am super worried. In a little while I will be getting a new kitten. I am super excited about it. My other 2 cat’s though, I am really worried may harm her or even kill her. They even try to get at my mother in laws cat under the door. They have only done that once, but still. My mother in laws cat also tries to attack them so maybe it will be different? I’m just really worried....