There's a universe where Han, Luke and Leia are dark, and the other verse where they're not.
The Luke from the light 'verse gets swapped with the Luke from the dark 'verse, and/or, he just ends up in the same place as him, or even dark!verse Luke dies. Light!Luke is still young and rather naive.
Dark!Han LOVES light!Luke, wanting to preserve his lightness as the whole naive farm boy thing turns him on like woah. (Maybe he and dark!Luke have been in a relationship for years and he'd be okay with this, or dark!Luke never reciprocated Han's feelings as he knew it would always keep him drawn to the light.)
Dark!Han seducing light!Luke and being really loving with him, but also a little creepy and a lot possessive.
Bonus for Dark!Luke seducing Light!Han (and Light!Leia totally knows what's up - that's not her brother, well, not quite).
Han/Luke, light/dark realities, light!Luke swapped with dark!Luke
There's a universe where Han, Luke and Leia are dark, and the other verse where they're not.
The Luke from the light 'verse gets swapped with the Luke from the dark 'verse, and/or, he just ends up in the same place as him, or even dark!verse Luke dies. Light!Luke is still young and rather naive.
Dark!Han LOVES light!Luke, wanting to preserve his lightness as the whole naive farm boy thing turns him on like woah. (Maybe he and dark!Luke have been in a relationship for years and he'd be okay with this, or dark!Luke never reciprocated Han's feelings as he knew it would always keep him drawn to the light.)
Dark!Han seducing light!Luke and being really loving with him, but also a little creepy and a lot possessive.
Bonus for Dark!Luke seducing Light!Han (and Light!Leia totally knows what's up - that's not her brother, well, not quite).