Sun and Jin were married before flight 815 crashed on the island.
Even Jacob was at their wedding.
Then why (in the alternate non-crash reality) are they staying in separate hotel rooms, not wearing wedding rings, and the bad dude said that the $25,000 was his fee for offing Jin?
Did they marry secretly?
But then why did Sun’s dad get Jin to beat up her adulterous love interest before?
Sun’s dad obviously wants Jin dead, but why?
It remained as a mystery.