I'm Sorry Kang Nam Goo (2016)

Both start with a happily married couple but husband in this gets to find out his long forgotten parents are rich and in the process leaves the wife for another rich lady.

Both are daily dramas with 100+ episodes. Both feature a female lead whose husband dumps her for a new chaebol wife. The child of the female lead dies due to the negligence of the new wife. The female lead tries to find justice for her dead child while the ex husband tries to cover up the truth. Both of these dramas provide the chance to love to hate the ex husband while cheering on a new romance for the female lead.

Both are 100+ episode revenge dramas. Plots are similar: death of a child, stealing of husbands/boyfriends, etc.