emoji is not listed in the add keyboard

My friend cannot see emojis when i am texting him. Upon looking at his phone(iphone 4s ios 6) and trying to activate it on the settings, the same way i have activated mine. i didn't see any emoji on the list and all he can see is boxes when i am texting him. But, my other friend who is using iphone 3g with an ios of 3, she can receive and see emojis as it is and not just a box even emoji is not installed. Why does the iphone 4s doesn't contain emoji in the add keyboard option? Is there something wrong with the phone?