Shyness is related to introversion, but that doesn't mean introverts are shy. How ? I'll explain that.
An introvert parent can be aggressive, and complain that his child is taking initiatives. A child can actually FEAR to be initiating, and this fear can be increased by extroversion (because lack of initiative goes against his cognitive preferences) ; statistically, shy persons are actually extroverts (sic). My father is an aggressive and pushy ISFj. As a child, when he told me off, I felt shy.