In both the series, the main couples start as friends with benefits but end up falling in love with each other.

The relationship between Fahlan and Sherbet is similar to that of Prapai and Sky because it begins with sex which cannot be forgotten by one of the parties who then starts chasing the other party and the relationship gradually develops into something serious. Both series include hot 18+ scenes.

In both the dramas, one from the the main characters is gay and the other one is bi. The relationship of the main couple is complicated and basically begins with sex but later turns into something more serious.

Transplant is a sequel of Manner of Death with the same main couple.
Both series include a (BL) romance but also a thrilling investigation that puts the main characters in danger.

Transplant is kinda a spin-off of Triage because Transplant's main caracters appeared as guest roles in Triage and they mostl likely are from the same creators.
Both series are BL dramas from the medical environment and there is an investigation of suspicious surgeries.

Both series include a main character whose parents die, he is then adopted by a new family and later falls in love with his stepbrother. One of the stepbrothers in each of the series initially refuses the other brother's affection because he does not want to disappoint their family but after some time he surrenders. In both dramas, the parents refuse to accept the relationship at first, so the couple has to persuade them that there is nothing wrong about that.
HIStory4 has a darker vibe because one of the characters uses morally questionable means to get his stepbrother's love.

Both dramas have a character of a Fujoshi girl who writes a fiction about boys she knows and her ship(s) eventually become(s) real.
Both shows are funny and entertaining but also can make you cry at certain moments.

In both series, the main couple consists of a human and a ghost. The human helps the gost to understand how he/she died and in the process, they fall in love.

In both series, the main couple consists of a human and a ghost. The human helps the gost to understand how he/she died and in the process, they fall in love.

In both series, one of the main characters uses food, especially Thai desserts, to win the heart of his love interest.
A romance between a cute guy and a cool guy

Both series have a powerful side character of a terrible artist manager who makes serious problems not only to the actor she is supposed to take care of but also to people around him.
Also, the series have a similar vibe, they are both quite light-hearted and entertaing, although the behaviour of some characters may annoy you.

Both shows take place in the entertainment industry and one of the main characters is an actor who is forced to hide his private life before his fans so that it does not destroy his career.
Both series are entertaining and sexy.