to make a distinction between Ruusan and Tari, I will now be using they/them for Ruusan. Tari will remain she/her. both twins have no concept of gender as they grew up Mandalorian and the distinction between men and women doesn't matter
the twins are opposites -- where Tari is anxiety riddled, Ruusan is confident. Tari is quiet (usually) and Ruusan is...loud, but no necessarily in volume kind of way. Ruusan loves to fight and Tari avoids them (not because she isn't confident in her abilities, when in a fight she's great and loves doing it, but in her opinion avoiding a fight saves a lot of time and effort and she'd argue it's just her pragmatism showing). where Tari loves secrets and won't tell them unless you exchange one in return, preferring subtly and being able to get in and out of places she shouldn't without anyone noticing, Ruusan prefers a more straightforward approach. Tari is bright and cheerful (or at least she tries to be), Ruusan is standoffish, aloof and quite cold
and I suppose if we're gonna go down the trope road -- most people might assume that Tari is the sun, as she tries to be bright and cheerful, in truth it's Ruusan. she's bold and brash and want to be the center of attention. Tari is the moon, quiet, quick and subtle. Ruusan draws the attention away from Tari, which Tari finds deep relief in
(yet in a summer/winter dynamic, Tari is summer and Ruusan is winter)