That must all be on the BD :o)

I'm thinking some very faint foreshadowing of the twins might work in the case of Vader. Esp. If alternates and deleted BR extras provide more.

In Tat orbit, Vader could stop and say something like "I know there's something... more than one...?" On the DS a vague mention of multiple disturbances and in reference to Leia "Even some who are not adepts can can show remarkable ability to draw strength from the Force.

I thought Tarkin could say something like "Everything about you is illigitimate-adopted daughter of the rebellion." Ben's reason for seperating was that together they were making too strong of an impression, so he went off to deactivate the beam (maybe sensed that luke would seek Leia, too.) Ben or Leia (hologram) mentioned that Leia came to Tat because she sensed she could find help there. (These are probably beyond fanedits.) :)