Easiest example where not all protagonists find "someone else" is The Lord of the Rings. Of the nine members of the Fellowship, Aragorn and Sam are the only ones who marry within the course of the novel. Merry and Pippin are mentioned in the appendixes to have found wives later, but that is not part of the plot per se. Legolas and Gimli remain bachelors for life, though that too is mentioned in the appendixes - their romantic life, or lack thereof, is not a part of the plot. And as for Frodo - it is very much part of the story that he cannot return home and settle down. He's been through too much. He gets Valinor instead.

If your protagonists are looking for love, then yes, the story would be incomplete until they've found it. But it could well be that they are not looking. Not looking yet, as is the case of Merry and Pippin, or not looking at all as is the case of Legolas, Gimli and Gandalf.

In our mind, we think of finding a mate as "settling down", it's a sign that "adventuring is over, everything will be fine, nothing is missing". But it might be that your character is not interested in settling down - they would rather wait for the next adventure. Consider Sherlock Holmes - he never marries, there's always the next story. Or it might be that you indicate "settling down" in some other way, letting the character find something else he's been looking for throughout the story - a new job, for instance. Finding love is something that can happen to the character later, not within the scope of your narration.

You need to provide each character some sort of closure. But this closure doesn't need to be in the form of love.

Everyone gets something, but it doesn’t have to be romantic.

Perhaps one MC gets his/her dream job in London and must move. That person would be leaving friends behind, but a new chapter of his life has begun. Cause for celebration and off he/she goes to London.

Another might discover a passion for something and choose to change the direction of his life - join the Peace Corps kind of thing.

Some might decide that they are not ready to settle down. Maybe in five years they will revisit the question, but they love who they are and what they are doing and are following the if it ain’t broke, don’t fix it adage.

Whether your novel is in the Romance genre or just a book where romance is the central topic, it's all about how you define your characters and their goals.

We the readers need to know what would make them happy. At least what the characters believe will make them happy. If the reader assumes what they want is love (in the mainstream sense of settling down to a happy coupled relationship) then, when the character doesn't get that, the reader will not consider it a happy ending.

Perhaps one character wants marriage and children. In mainstream work, this is exactly what she would get (if the ending is happy). But you can show the reader that her real focus is being a mom. Then if the book ends with her pregnant with a co-parenting arrangement in place with the dad (they could buy a duplex together), that could be over the moon happiness for all of them. With proper foreshadowing, the reader will accept that too.

In other cases, you can show that the dating arrangements among the 4 was a valued and important learning experience but not what any of them wanted longterm. You might want to frame something like this with the characters happy (and/or happily coupled) in the future and maybe still in touch but not together (or make a reunion 20 years later). With the framing, the reader will not expect the characters end up with each other.

Note: With the caveat that the Romance genre is pretty specific about the arc of a story and your alternatives may not fly there. I realize it's not the genre you're aiming for but wanted to mention it for others.

A story about someone ostensibly looking for love can resolve without them finding a romantic partner if it turns out that they were actually being driven by a motive other than to find love. There are lots of reasons people look for or invest in relationships besides the desire for a romantic partner. Some examples:

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  To feel validated. People naturally have a strong desire for social approval. A relationship is way of confirming your value to others. If you're in a relationship, you've proved to yourself that you're at least valuable enough for someone else to be committed to you. A character's need for social approval might manifest as a search for love but can be resolved by them finding that approval through other means. Perhaps they realize the relationship wasn't actually what they needed and they find fulfillment by playing an active role in their community or some other group


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  To avoid facing their own problems. Instead of facing our issues, we can justify them by finding other people with the same or similar problems. For example, a character with reluctance to establish discipline and direction in their life might just consider themselves spontaneous and carefree and be attracted to someone with similar qualities. As the story progresses and the character develops, maybe they realize they need to start making some hard decisions in their life and rather than being motivated by romance, they were attracted to someone else who made shirking off responsibility feel OK.


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  To conform to an incompatible role. Lots of people end up in relationships because they feel that "I should be married by now". Or it could be expected from their family or culture that they're in a relationship by the current point in their life. This would cause them to seek out a relationship to avoid feeling like an outlier or a failure. This type of story could resolve by them realizing that their personal needs are more important than adhering to tradition or whatever other expectations they tried to meet.


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  As part of personal exploration. Someone with little or no relationship experience doesn't know how having one will affect their life. A character might date or be in a relationship that ends but still achieve resolution by gaining insight into how a relationship fits into their own life. It could turn out that that they're not prepared to sacrifice some of their freedom yet or to have someone else intimately affected by their actions.

Another possibility is that the relationship leads the character to realize something about themself that allows them to pursue something more personally valuable than the relationship initially was. For example, Joe might be a typical starving artist - full of talent, but unable to catch a break. Perhaps the reality is that he has every opportunity to succeed but is actually the one holding himself back. Joe's romantic partner might be the only one who can reveal this to him, either because they're the only one Joe trusts enough to believe or because they're the only one close enough to him to realize it.

Almost every ending to a romance is cliche

An ending needs to provide closure for your characters. Whatever their motivation or journey through the novel is, at the end they need an ending. When writing romance the most common ending to finding the love they were looking for, but that isn't the only one.

There are of course a variety of sad endings you can choose from. Character death, separation or other trauma are all common and somewhat cliche. Other happy ending are also available though.

A popular alternative to the "finding love" ending is the "self realisation" ending. The character doesn't find love, but that's ok, because they learned to love themselves. Often these stories are more about a characters internal struggles with love than a traditional love story. The character learns about themselves and what they value and maybe love wasn't what they were searching for afterall. This is still a somewhat cliche ending but it is a happy one.

Another approach is to leave your character still looking for loving, but they gained something along the way. Whether they learned something about themselves, helped someone else, literally gained some object or goal, whatever it is they are better for it. This ending is the cliche ending of hope. Sure the character hasn't found what they were looking for yet, but because of the events of the novel we are more hopeful for the future.

With apologies out front I'd like to mention the series ending of "Frasier", arguably a show with emphasis on relationships succeeding and failing. Apologies since if I'm siting TV stories I'm likely to have skipped something.

The last show has Frasier in an airline seat telling a seatmate the story of how his current relationship finally had a crisis and ended. This had to do with his choice to take a job in a new city, Denver say, hence air travel, causing the girlfriend to go back to Chicago.

His presence on the plane implies the choice he made while the reasons unfolded painfully. As he finishes explaining the reasons, choices and necessity of his heartbreaking choice the show ends with the stewardess announcing "Welcome to Chicago". "Hey, I thought he had given up and gone to Denver!". The surprise is delightful. While the problems are not solved you can tell that he has not given up. More importantly, you're not going to see how it ends up, we're done here.

At the end of some Harrison Ford CIA movie he comes home after much action/adventure. Arriving in the kitchen he asks his wife if she has learned the sex of the upcoming baby. We cut to her and see her smile. We cut to him to see him look at her questioningly and that is the end of the movie.

An ending is only the end of our view, our window into the lives of the characters. Allowing them to "Get on with their lives" on their own is, I think, the best.

Yes it can happen that one or two do not end up in a relationship and are happy.

There are loners out there who are much happier by themselves than they are with other people. For them the thought of coming home to a blissfully empty house is what they look forward to all day. They might like there beginning partner and want them to be happy. Thus, their partner finding a relationship so they aren't obligated to be that relationship may be their happy ending.

Just have two people in the group who are like that and you have it set.

An alternative, if that seems to be too much of a coincidence, is to have one or more people in the group beginning a relationship with someone outside the group. It might take them from the group (or add a new member) but if they are happy and the group does not have to remain static for story purposes, that's still the happy ending you were looking for.

I think you can have a satisfying conclusion to such a story if not everyone gets married or otherwise committed, but everyone's final status is explained. If the story ends with one of the main characters deciding that he doesn't want to get married because he wants to devote his life to making music or exploring Mars or whatever and a wife would be a responsibility he is not prepared to take on, I think that could be a very satisfying and happy ending. Or if the story ended with two characters breaking up, it could still be presented as, he got out of that toxic relationship, and now he is prepared to get on with his life. Or, the story doesn't have to have a 100% happy ending. Perhaps several of the main characters end up together but another is left alone, and the story ends with him being disappointed but saying that he will try again. Etc. (All my "he"s here are the generic "he". Obviously any of them could be a "she".)

Romantic stories often end with less-central characters left alone. A very common romance plot is, heroine must choose between two men. Usually the man she doesn't choose is left alone at the end of the story.

There are lots of ways to end a story. Sure, a romance novel that ends with the hero and heroine breaking up and going off in different directions would be unusual, but not unheard of.

Nicholas Montserrat's The Cruel Sea falls into this category.

The main PoV character (Lockhart) is engaged, and his girlfriend is pregnant. She dies in an accident while he is at sea. A number of secondary PoV characters die mid-book, or (Ferraby) are too damaged to continue; Ferraby is married and has a child, but this contributes to his breakdown (possibly the first representation of male post-partum depression in literature?). The captain, Ericson, is married and presumably returns to his wife at the end, but he has a rant towards the end about how he's reached a point where he can't consider any humanity in what he does any more - all his men are just cogs in a machine for him now.

And yet it's a happy ending, because the war is over and there's relief from all the survivors that they made it to the end alive.

Three Separate questions? Okay.

Are there examples where this does not happen?

Sure, there probably are. I mean, look at Sword Art Online... I don't think Klein ever wound up with anybody did he? Or what about Agnil? It's just more of a question of how can you do so well.

And if so, how is the incompleteness impression avoided?

Make your work as complete as possible. If everybody needs a relationship, give them one. Many Potterheads thought Harry and Hermione would wind up together. We see that was wrong. Harry wound up with someone we didn't quite expect, but whom there was a basis for a relationship between them. That said, if a relationship isn't necessary, make sure it's clear to the audience that at the end of everything, your character is happier without a relationship.

How, specifically, can I guide the reader so that he is not dissatisfied if the "typical" ending does not occur?

The specifics are determined by your characters. We can't answer this blindly. Give me a character, their experiences, and so forth, and I can tell you how to guide to this conclusion, because the answer is not clear-cut otherwise.

Coming of age, finding love in yourself

Your story can also be a coming of age story or rather coming to terms and accepting that a character is better off alone. It could be a very happy ending a character ends up accepting himself and his inability to find love. He learns to love himself.

The human condition: the search never ends

Or, it could be about the human condition that everything ends as it started coming full circle, reflecting the human aspect that we are always looking for answers. Whether we find them or not is of secondary importance to the story.

Write an ending at all?

Sometimes you don't want to provide the conclusion even cut off the climax, letting your readers fill in the rest, because the result comes so close to them. An ending is not necessarily needed in writing if the result is a logical conclusion, unless you want provide one last twist or something.

Resolution for your characters or for your readers?

Is your story about the characters, or do you want to hit home with the readers. Depending on your answer, do the characters really need happy romantic resolution?

I guess I should start off by saying SPOILERS

I don't know how much time you want to invest into figuring out this aspect of your answer. On one end of the scale Dickens' Bleak House might fit what you're looking for. John Jarndyce loves Esther Summerson and is engaged to her but, realizing she loves another, finds satisfaction in helping them to have a happy life together. There are a number of other threads with other minor characters, some of which end happily and some otherwise. The arcs are, in general, satisfying so there are plenty of ideas here. It is a long book so reading through it and thinking critically about it will take some time.

On the low end of the scale is the movie My Best Friend's Wedding. A standard length romantic comedy where the heroine does not get the guy at the end. She gets a friend and she accepts that the guy is really better off with someone else.

In both of these cases the key, as I see it, is that the protagonist has solved the relationship problem to his or her own satisfaction. It doesn't have to be, as in these cases, "I'm happy he or she is happy with someone else" but what gives the reader the feeling of completeness is having the character arrive at a place of happiness and stability.

There is also the series of novels A Dance to the Music of Time by Anthony Powell. Twelve novels, largely about the same set of characters. People enter and leave the story and fall in and out of love. Some parts do seem a bit unfinished, the idea being that it is reflecting the way we meet and lose touch with people in "real life" and don't always hear the end of their stories. You may or may not want to go this route.

I know there are a lot of answers already but I think what you’re looking for is, at the end of the story everyone should get closure.

Here’s the definition of closure:

the feeling or act of bringing an unpleasant situation, time, or
experience to an end, so that you are able to start new activities

If a significant character on the story doesn’t get it, then the story would seem incomplete.

Note closure doesn’t involve necessarily love relationships or any other definitive action but is more about the definition above, closing to be able to star something new. That covers all the examples given on all other answers.