No Gain, No Love (2024)

Both have Older woman/younger man plot and the leads have very natural romantic and friendly chemistry.

In both dramas main leads get into contract relationship for the for their benefits and ends up loving eachother.

Nothing similar just Penthouse Siblings in this drama together. It's a romantic comedy drama. quite good.

NGNL is still on-going but both have the trifecta of female friendships and dealing with each character's romantic relationships.

A contractual marriage ends up in a romance. The ML falls first. The FL has a bad relationship with her mother.

Both star Shin Min Ah, and involve a spontaneous/quick marriage at nearly the beginning of the show.