Proposed Luke “Sister” storyline.

Obi Wan talks to Luke and he mentions his twin sister. The conversation ends after Ben says “your sister remains safely anonymous…”

Luke and Leia’s conversation on Endor (after Luke says that he must leave to confront Vader):

“He’s my Father”

“Your father?”

“The Force is strong in my family… my father has it, I have it, my sister has it…”

“No! Luke, run away. Far away!”

And the rest of the conversation continues as normal with Han stepping in to hug Leia (without jealousy)

Luke’s sister isn’t mentioned until the end by Vader.