There's also a more passionated kiss between Luke and Leia, a brief moment of it can be seen in the original trailer. I don't know where that scene would be, it looked like an alternate version of Leia's kiss, but didn't work as well as the surprise kiss one. Perhaps they already knew Leia was Luke's sister, and thought that a more passionated kiss between siblings would be waaay too much for a PG film. It would be ok in a early 70s Jonh Waters film though.