When I was very young, my household called the genitals tween. Which got kinda weird when I was older and they (american marketing started calling children between the ages of ten and twelve 'tweens (instead of preteens). I think part of this is that my parents were quite young, but I dunno. My stepmum had an old (like, from the 90s, I guess sex-ed book that she left next to our encyclopaedias and told us that we were welcome to read it. Which is a bit passive, but probably at least a little more open than some parents.