I feel like Romeo and Juliet keep secrets from everyone, mostly their family members, because of their families hating each other. They never tell us why the Montagues and Capulets are mad at each other so i’m guessing they dont tell their children either. If their parents lie to them and to other people, their kids are going to learn from it pretty quickly. And they are also teenagers, A teenager tells their parents whats going on in their lives but not all of it. Its not like your parents are telling you everything about their childhood, and all the weird stuff that they did back then.