Both SMLs are morally gray and were in love with the FL since childhood but end up marrying her to the ML for personal reasons. Both FLs struggle with trusting the ML, and at one point stab him. Both dramas are historical and have a similar tone and pacing.

Both are sci-fi disaster movies in which a group of strangers are trapped in some form of transportation (train vs. vehicles on a bridge) while mutated beings try to kill them. Both center around an estranged father-daughter relationship.

Both are mini dramas in which the ML is undercover in a gang and the FL inadvertently becomes caught up with the gang, under the ML's protection. There is a SFL who is part of the gang and tries to seduce the ML.

Both MLs are undercover in a gang and the FLs are kidnapped by the gang. The ML protects them.
..........................................

Both are historical dramas and have an intelligent and strong FL who solves the difficulties and hardships of her family.

Both are historical dramas in which the FL is destined for an arranged marriage she wants to get out of. Both MLs are lying about their identities.

One is the drama, the other an epilogue.
......................................................................
.............................................................................

Both involve one of the leads caught in a time loop trying to change events and save the life of the other lead who has died in their present.

Both involve the FL time traveling to the past and trying to change events to prevent the death of the ML.

Both involve one of the leads traveling repeatedly between past and present to change what happened and save the other lead, all while unravelling the mystery surrounding their death.

Both jump between past and present as one of the leads in the present tries to change the past of their high school years and prevent the death of the other lead.

Both are historical dramas in which the ML is a human who is in charge of hunting down demons/another people of which the FL secretly is. Despite this, the two fall in love.