But, even if a pair of twins share their rising sign, there's no astrological reason for their personalities to be carbon copies. You probably don't behave just like someone who happens to share your sign, and the same goes for siblings that share planetary placements. Come to think of it, maybe that "set" of personality traits we mentioned earlier is less of a checklist and more of a spectrum: No two Scorpios, for example, exhibit the same exact traits in the same exact way. So, even with all the same signs between them, there's a pretty big chance that two twins will express them differently. If you need more proof, just watch a few episodes of So Little Time.