from my understanding, northstar and aurora's powers are essentially the same, so i give them similar quirks, habits, & hcs -- hypopigmented skin, silver freckles, silver specks in their black hair, pointed ears, as well as traits like impatience, recklessness, quick temper, anything related to being fast and bright, as well as them both tending to use french casually; they're twins, so they have the same big threes of zodiac too, and i like to imagine that neither of them knows who the older twin is, it just depends on their mood and who's in trouble more.
that said, their personalities, motives, and actual behaviours are not the same, and there are some core differences like: northstar is faster than aurora & the fasted mutant in general, aurora's lights are brighter and more diffused and ethereal-like, their ears are expressive like cats but in different ways & are sensitive to touch in different ways (i'd even go as far to say jp's ears aren't that sensitive), jp's use of french is more dramatic, while aurora uses french to be formal and distinguished. although they live together, aurora is more outwardly averse to wealth, luxury, socialisation, and the like -- but not entirely, either, it's something she'd need to stop feeling self-conscious about first. jeanne-marie also has the patience to actually read, write, and sit down with things, with northstar absolutely lacks, making him horrible at meditation and reading comprehension, while aurora excels at both extremes (speed and stillness), making her the more tolerable one of the pair