My parents only ever needed to threaten us and we got into line. You can't discount the power of a well-practiced glower. I use that skill (apparently inherited) on my nephew and the students where I work - ages 2 through 22, it works.
OTOH, between the three of us girls, there was all sorts of physical violence. Usually for no reason more than "she looked at me funny" or "she was breathing my air".
