maidenholmes:
Are you only looking for arranged marriages imposed on the couple by someone else?
The majority are probably where the couple is faking a marriage for whatever reason (dying grandpa wants ML to be married, marriage faked so lead can stop going on blind dates), etc.
Yes, imposed marriage primarily. Maybe because of some old promise (Goong, Sweet 18) between grandpas. Promise made even before they were born.
Or some circumstance makes it so they have to wed, like they accidentally fall a sleep in the same room or in same bed, and are forced to marry by their parents in order to save the family honor. (I believe this is the premise of Delightful Girl, Choon Hyang)
Either one of them or both are opposed to it, but since this is romance dramas they start to fall for each other.