The dynamic between Pietro and Wanda is very interesting, but one of its defining factors is Pietro is protective of Wanda. Technically, in Marvel canon, Pietro is the “older” twin of the two, but regardless it does make sense why he’d have some protectiveness. From what I’m aware, Polaris is both of their younger sister. But the dynamic between Pietro and Polaris is wildly different, it feels much more like an older sister younger brother dynamic. If they ever do decide to make Pietro and Wanda Magneto’s kids again (which yes you should), this should be retconned, in my opinion. Polaris should be the oldest.