None of these fit exactly, but:
- Ms. Perfect - Sung Joon's character is arguably the SL. He falls for the FL, who gets a divorce during the course of the drama. Her ex-husband continues to have a relationship with the kids, but the SL ends up with the FL and they raise they kids.
- Marriage Contract - the bio dad has passed away, so he doesn't come back to cause problems (his mum sort of does though)
- Madame Antoine - the FL is divorced, has a kid, and ends up with the ML, but her daughter lives abroad and moves in with her ex-husband
Edit: also these are historical dramas with very different dynamics, but maybe the King's Woman and arguably Empress Ki