That would hurt
It seems like this five-year-old still does not know human biology well enough to be making threats, especially ones like this directed at a female. Also, why is this kid threatening their parents with violence in the first place? What is making them act out with such forms of aggression?
We guess that question will never be answered but we hope that this kid found inner peace and stopped making threats. Your parents love you, you do not need to claim that you will kick them in the groan if they make you go to bed. Sleep is your friend kid, remember that.