Day(R)

Sun is a golden she-cat with gold-brown stripe down her back and across her ears and green eyes.

Moon(TNC)
She don't appear at all, but is losely mentioned as Moon referred to his comrades, which he meant as the Mist Cats, and Day is one of the Mist Cats.

Sun(TNC)
She appears in the prologue, reporting back to Moon along with the rest of the Mist Cats.

Family
Brother: Night; spirit (as of  Sun)