every vampire sparkles. that's why volturi have their cloaks so it wouldn't notice in the middle of the day... renesmee and nahuel and his sisters glow cause they're half human half vampires...
All vampires sparkle in the sun. Like in New moon, in italy alice had to wear a glove thingy on her arm, so she wouldnt sparkle in the sun, and give away the species of vamps.
Basically, all vampires in the "Twilight series" sparkle in the sun - no matter whether it is Edward, Alice, another Cullen, a Volturi or a nomade vampire.
They all sparkle. That's supposed to be like the point that they are so different and "monsters". So to prove that point the all sparkle. Except I think they ruined it in the movie.