Even if the writer chooses to challenge that assumption, e.g. Take a Third Option, Marry Them All, or Polyamory, there will be some pretty tricky footwork required to make it all come out to a resolution.
- 1: Alice wants both Bob and Charlie, but cannot decide which. Both are unrequited or their wishes are unimportant at this point. This is the classic Betty and Veronica trope.
- 2: Alice wants Bob, Bob wants Claire, and Claire wants Alice. Sometimes referred to as a Bizarre Love Triangle, after the New Order song. It can involve as many people as you like, turning it into a square, pentagon or more, but ultimately the love remains unrequited.
- 3: The classic love war setup. Bob and Charlie want Alice. Alice is neutral toward, or not initially thinking in romantic terms of Bob and Charlie, or thinking about them at all. Not a bad situation to be in, if you are Alice, though obviously a bit less so for Bob and Charlie. Some Alices will be tempted to see if there is any Type 7 (below) potential in the situation.
- 4: Alice wants Bob, who is already in a relationship with Claire. Bob is unaware/neutral (leaving Alice as a Hopeless Suitor), or is aware of the interest and can't/won't reciprocate (leaving Alice in the "friend zone"). As the most complicated set of relations which is compatible with both monogamy and heterosexuality, this is very common.
A sub-variety of the Unwanted Harem often crops up in the Harem Genre, where the main character has a preferred Love Interest, often the first girl, plus a bevy of also-rans vying against the main Love Interest for the protagonist's romantic attention.
- 5: Alice loves Bob, but Bob loves Claire. Claire doesn't have feelings for either. Alice might try persuading Bob to give up on Claire. If Alice is Ax-Crazy (or otherwise extremely jealous), she might attempt to Murder the Hypotenuse. Alternatively, Alice might just want her beloved to be happy, and try to set Claire up with Bob. This is the smallest situation directly involving at least three characters where All Love Is Unrequited. This can potentially involve more than three people, with Claire having feelings for David, David having feelings for Eric, and so forth.
- 6: Alice wants Bob and Claire, who are already in a relationship. In this one, the "want" may or may not be sexual in nature—this could just be a platonic thing. Pair the Suitors is what happens when a type 1 or type 3 turn into a type 6.
- 7: The classic "affair" set up. Alice is in a relationship with Bob, but she's also in a relationship with Charlie. Either Bob and Charlie don't know about the other's involvement at all or Charlie knows he's the secret lover and acts accordingly. Much of the drama/comedy comes from all the work needed to make sure that the space between B and C stays free from any sort of information flow. A lot of geography between the two helps, or maybe a good social divide.
The Harem Genre usually sits here as well, with multiple Love Interests romantically involved with the protagonist (usually several females vying for a single male, though other variations such as the "reverse harem" exist). How it plays out varies by work: Sometimes a harem series ends on a Marry Them All note (which can become a type 8 in rare cases where the love interests are in love with each other, too), while in rarer cases the primary of the harem picks one to stay with and abandons the others, shifting the situation to a type 4 Unwanted Harem. Oftentimes, however, there's No Romantic Resolution, though this is frequently because the series was adapted from another medium and was Cut Short relative to the source material.
- 8: When all three parties are devoted to each other in some manner. This needn't be sexual, but this is the type that's the most compatible with polyamory in its various forms. The most obvious example is a straight-up threesome: Alice, Bob, and Charlie are happily in a relationship together.
- 9: Bob and Charlie are close with each other but are also attracted to Alice. Bob and Charlie might be best friends or siblings, and much of the conflict comes from wanting to pursue Alice but not wanting to hurt the other.
- 10: Alice and Bob are in a relationship, but Bob is attracted to Charlie. How sympathetically Bob is played often depends on their gender.
- 11: The classic affair set up with a twist. Alice is in a relationship with Bob and Charlie, but Bob becomes attracted to Charlie. Bob and Charlie may or may not know about the other's involvement with Alice. This situation is clearly the fault of Alice, who failed to control the information flow properly.
- 12: Alice and Charlie are in a relationship, often married, but Alice likes Bob and Bob likes Charlie. Depending on genders this can be a hilarious or very tragic set up.
- 13: Alice must choose between Bob and Charlie, but Bob is also attracted to Charlie. The non-sexual setup might be something like a boy having a family member get in the way of his relationship.
