You need to think about the chemistry between the characters. Make sure the actors can convey the depth of the emotions convincingly.
Well, first off, the physical appearance and age of the actors should match the characters in the story. Also, their acting skills are crucial to bring out the nuances of the love story. Another important factor is their ability to work well together on screen.
When choosing the cast for a love story, you have to look at their ability to connect with the audience emotionally. Also, their past performances in similar roles can give you an idea of how well they might fit. And don't forget to consider their popularity and fan base, as it can influence the success of the story.