Love the topic!
I can't remember when DD started understanding the differences (Before she was 16 mths) but I do equate this is 2 things:
1. her use of pronouns has been perfect from the start. (Before 9 mths old)
2. my willingness to talk about body parts even those that are different. The general pop. tends to find this a taboo topic and stays clear of the conversation when might be why the recognition of the opposite sex is at 30 mths) From an early age she would run around poking her chest out proclaiming that she had 'boobies' and question where her daddy's were. Questions lead to realization that things are different.
