By example, teach your children that “no” will be respected if they do not want to be touched (ex. tickling, hugging, or kissing). If your child says no – stop. And tell them you stopped because they said no. Don’t make them hug, kiss, or engage with people if they are uncomfortable, and if they are telling someone no or to stop (even if it’s grandpa) and that person is not listening – stop them and explain why it is important for your child’s safety to respect them when they say “no.” Let them know they can say no to anyone – a teacher, a coach, an older kid, etc. if they are trying to do anything involving someone’s body that they don’t like or know is inappropriate.
And again, we must teach our children that if someone else says “no”, they must respect that as well and stop if they’re doing something that is making a person mad, scared, or sad.