Home for Summer (2019)

Both start with married couple having difficulties following infidelity as husband is seduced by random rich girl eventually leading to divorce and wife reaching new heights with support from main protagonist.

Cheating partner, rich chaebol lady, single mom, falling in love with the villain's brother, there's just so much in common between the two!

Both involve married couple and husband cheating on the wife by leaving the spouse for a rich girl who started the seduction from her side first.

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.

Same writer and same director kbs1 dailies.
An adopted child involved.
Many common supporting actors.
A writer supporting character.
A salon opposite a restaurant.
(Bonus: the main actors in BML resemble the actors in HFS: Yang Byeong Yeol (BML) resembles Yoon Sun Woo (HFS). Nam Sang Ji (BML) looks a bit like Lee Young Eun (HFS). Cha Min Ji (BML) looks a lot like Na Hye Mi (HFS).)

In both these dramas, the main character adopts a child and does her best to protect and raise him. The main characters are betrayed by the men in their lives, but they meet someone new that loves them and their adopted child. The adopted child's birth families are terrible awful people in both dramas. The main character has to fight for custody with the birth families.

In both these dramas, the main characters husband cheats on them and divorces them. Both the main characters meet someone new and fall in love. The cheating husbands are miserable with their new wives lol