Love triangles only work when three people love each other. Two people will romantically love a third, but the first two have to love each other platonically. The lovers are conflicted, not only because they are trying to catch the attention of their beloved, but because they do not want to hurt each other.
Cyrano de Bergerac is a classic example. Cyrano and Christian both love Roxane, but they also care about each other. Cyrano gives up his suit for Roxane in part because he wants his friend Christian to be happy. The conflict comes from Cyrano’s self sacrifice for both of the people he loves.
Twilight is not a love triangle, it’s a rivalry. Edward doesn’t leave Bella because he wants Jacob to be happy; he leaves her because he thinks that’s what’s best for her. His priority is always Bella. Any time he works with Jacob, it is solely at the request of Bella for her benefit. The driving force is always Bella.
I could make one of these for all of John’s dates, but you get the picture. John wants Irene to tell Sherlock that she’s alive, not because he cares about Irene and wants her to have a nice happy life with Sherlock, but because John thinks that Sherlock loves her and that will make him happy. His motivations are entirely driven by Sherlock’s needs.
This is a rivalry. Sherlock’s actions through S3 support John. Everything he does, he does for John. He plans the wedding rather than go out on cases for John, he teaches John to dance, he arranges the meet-up at the empty house for John. If Sherlock wanted to help Mary, he could have easily done it without involving John. If he truly shot Magnussen for Mary, why not bring her along? She’s a trained assassin! Surely she could be some help. Yet he drugs her and leaves her at home. He excludes her because it’s not done for her benefit. He does not love her, platonically or otherwise. Sherlock backs away from John romantically not because of his high regard for Mary, but because he wants John to be happy. Mary benefits only because of her attachment to John. Sherlock’s sole focus is John’s safety. Mary compromises that, so Sherlock moves to protect her. Without John, he wouldn’t. Sherlock does not care about Mary.
Years ago, I was chatting to someone who was a temp at my job, and she mentioned that her UK boyfriend’s family were “nice, but there’s this other branch who were notorious gangsters in the ‘60s. I think there was a movie made about them.”
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