My friend Cheyne and I used to have a roleplaying game going where Omi, Shuichi, Hisoka and Atsuro (from Kaikan Phrase) were quadruplets who got separated at birth (for vague reasons, mostly having to do with Reiji Takatori being evil). Had we been into X at the time, we probably would have added Kamui and had an even set of quintuplets.

Enjoy the movie. I'm dying to see it myself, but I'm holding out, because I plan to see it when I go visit my friend Sonya-chan in Canada in a few weeks.