Teens don’t usually ask their parents about those things unless they trust that their parents will not judge them and instead provide guidance and wisdom. I think telling them that their feelings and desires are inappropriate due to their age would significantly damage that trust. That trust is going to be extremely important later in life when they start to have sex because it’s important that they are comfortable enough to ask about birth control options. Also, let’s be honest about this. If they really want it, they’ll find a way to get it without you knowing.