I think that can vary by kid. At the very least, from a completely asexual perspective, and since these parts are normally always hidden, a young child could be

I think that can vary by kid. At the very least, from a completely asexual perspective, and since these parts are normally always hidden, a young child could be curious about the differences. My 21 month old knows the names of those parts and knows that mommy seems to be missing something lol. But he hasn't asked yet because he can't verbalize questions yet.