The child who’s origins are purposefully left a mystery, Ayanami Rei is a quiet girl who often keeps to herself. She resembles Ikari Shinji’s mother, Ikari Yui, and often acts motherly towards him, despite being (or "appearing to be") the same age. It is stated in the Red Cross Book that Rei was actually created from the salvaged remains of Yui after she was absorbed into the Unit 01 in 2004.
I’m not sure if Sanriotown moderators will mind posting a picture like this, but in case there is a problem, do let me know so I can take this down? I don’t want to make any trouble… But she makes a really impressive Rei!