Hmmmm...... I dunno. When Kurogane met Tomoyo there, he looked alot YOUNGER than 16 to me. Okay, maybe not much younger, maybe 2 or three years. However, Tomoyo almost seemed more mature ne? But then again, Kurogane just went through some traumatic events, you can't expect him to be acting normal. At lest Syaoran came back.
I can't imagine Tomoyo being anything
but mature - she's just that kind of girl. Especially in Tsubasa: Tomoyo-hime, being royalty, would naturally be mature; especially considering her gifts. I reckon Kurogane was supposed to be Syaoran's age at that point, and I think he's supposed to be about 16.
And as for Fay's past... Ah, I've almost given up hope u.u One day! And hopefully, one day soon. At least another clue, CLAMP-sama...?