Here's some trivia that is kinda sorta related to the topic, which you may find of some amusement.
So you know the traditional Harlequin romance novels, right? Especially the historical ones? Those things are formulaic as fuck.
This isn't a slam or an opinion. You can actually write the publisher of those romances and they will send you a document detailing the criteria which your submissions MUST follow if you want to submit a manuscript for consideration to be published as a romance novel. And they are VERY particular. Stuff like the heroine must be between 18-22 years of age, the hero has to be older but no more than 10 years older, the heroine must be fiesty and free-spirited, etc etc.
Of partial relevance to this thread is the requirement that:
-Any sidekicks of either the hero or the heroine must be unmistakably NOT a rival for the hero's/heroine's affections. That is, if the heroine has a female sidekick, there cannot be ANYTHING in the story which might lead the reader to suspect that she's making a play for the hero, or that the hero might have feelings for the sidekick. Similar remarks apply for any male sidekicks the hero may have.
-Any character who IS an obvious romantic rival for the hero/heroine must very clearly and unambiguously be a bad guy/gal.
Always thought that was interesting.