identical twins dont necessarily need to be same gender they can have the same appearence traits like blonde hair blue eyes and fair skin and be a boy and a girl
identical twins have to have the same sex as they come from the same egg, that's how they're identical. if they were born boy/girl twins, then they are fraternal and therefore not identical. that's how biology works. sure they can look eerily similar, or perhaps they were born identical and one transitioned into the other gender