my boyfriend's son. do I have the right to...

I have been with my bf for over 2 years. He has a hard time telling his son what to do because he has spoiled him for so long. The kid is 14 years old and he is with us every weekend. He asked his dad to make him pancakes and when his dad replied "no, just have some cereal because I'm exhausted.", he punched his dad in the arm and starts yelling at him. His dad doesn't do anything and this behavior is constant. I have seen the kid pull a knife out on his dad a few times or just curse at his dad when he doesn't get his way. It is never punished. Considering that I live with my bf, what do I have the right to say/do in these situations?