They had a plan, which ended in victory, but not survival. Death wasn't preferable but, sadly, was seemingly unavoidable.
They were always close, three of them, but the last year on the run, scared and alone, lugging around a horocrux of all Morgana-damned things, brought them infinitely closer together. In another world, jealousy and insecurity could've driven a wedge between them. In this one, the endless ocean of love they felt for one was matched, drop for drop, with the one devoted to the other. Their little, fucked up triad lacked a lot of things such as food and shelter and parental care, but not love. Never love. The boys worshiped the girl and the girl was equally fierce in her devotion to her boys. They belonged to and with each other and that was always how it was going to be.
Were they normal teenagers, living normal lives, or even if their mental states were even approaching sane, the process of figuring out and negotiating their relationship would've been a stressful, emotional, turbulent time. However, children being hunted in a middle of a civil war, with one functional set of parents between them, have a unique sense of perspective. The need for companionship and human contact overrode whatever self-conscious instinct they might have otherwise had, and shyness gave way to exhausted honesty. They faced death and mayhem since they were eleven years old, and trying to be coy with one another, trying to seduce or beguile would be both incredibly awkward, and somehow disrespectful to the bond they had built over the years.
Truth be told, while some would have found their relationship inspiring or romantic, it would be more accurate to say it was tragic. It was plain each of them suffered from a case of frightening but grotesquely functional co-dependency which alone would guarantee them trips to the mind healers until they were old and grey and able to fathom the notion of spending the day apart
See, magic is a tricky business. It's not just an attribute, not just a force as muggles would define it. It's not just pointing a stick and exclaiming broken strings of latin. It is emotional and mystical, unpredictable and uncontrollable. It reacts to wishes, strong emotion, iron will. It is shaped by belief, which is what makes it so difficult to articulate in a language shaped by rationalism and enlightenment. Wizards not muggles with a wand. Their magic shapes them, and their lives shape their magic. Where the muggles have science and theology, spirited debates about the nature or existence of the soul, the magical community has both ghosts and the soul arts, undisputable evidence of both souls and some sort of afterlife.
Now, as many a muggleborn has despaired over the years, trying to scientifically quantify magic, trying to establish a scholarship such as that of physics or chemistry, is not only impossible but redundant. Magicals and muggles are fundamentally different beings, whose vast difference has lead to sharp divergence in evolution, both mental and physical. In a very real and tangible sense, a nonmagical horse is closer to a nonmagical human than a wizard or a witch. They are physically, metaphysically and philosophically different. For example, a muggle child, age seven, sees fire for the first time, tries to touch it, gets burnt and while it is mentally changed forever with the newfound understanding of "burn" and "fire" and "hurt", physically it is more or less the same. The mental trauma only very rarely translates to the physical world. And because the physical trauma is the more immediate and deadly threat, the focus falls on it, and mental trauma gets a back seat at best if it isn't thrown out the window completely.
With magical children, things are altogether different. A magical child putting its hand in the fire will doubtlessly result in immediate and sometimes permanent consequences, but they will be as a result of the magic fueled by the child's fear and pain and anger. Because physical trauma is so easily fixed as a matter of hours or with the swish of a wand, all the focus is on the mental state. That is why magical children have to be monitored much more than muggle ones. The volatility and emotional strength of children coupled with magical ability result in a risk to the children and their surroundings.
Remember that child that stuck its hand in the fire? It could explode the fireplace in its anger, or apparate far away in its fear. It can form scales on its arm to protect it in the future, or even turn it to stone to stop it from hurting in the present. In the milder cases, it can develop a block on fire-based-, or an affinity for water-based magic.
Wizards are shaped by their emotions much more, which shapes their magic, which in turn lets them shape the world around them.
Now, imagine, if you can, a group of three eleven-year-old children, each with their own complexes and problems, which will doubtlessly already shape their magic in predictably sad ways. The attention-starved, grossly overshadowed boy, yearning to prove himself and earn the attention he wants. The abused, neglected orphan, wanting a normal life with someone, anyone to love him. The too-clever, emotionally stunted girl trying to find the right string of words, the right facial expression, the right behavioral pattern needed to understand why the other children are so slow, and why mommy and daddy are scared of her. All three of them horrifically socially inept. All three of them with magic shaped by mental scars instead of happy memories. Brought together by chance but tied together by surviving attempted murder. Which set the tone for the next ten or so years, with peace as a wistful goal and chaos as a devoted companion.
And that, really, is why their relationship is more sad than romantic, more unhealthy than inspiring. These children have been shaped almost exclusively by trauma, by narrowly avoiding death and dealing it. Always together, always surviving. By the time they reach magical maturity their magic is so twisted together, they are so viciously devoted to each other, that the notion of romantic love is almost trivial in comparison. Who was fucking whom held less weight to jaded-eyed teenagers who in a very tangible way, shaped each other's souls.
So, they approached this final danger, this Last Battle as they did everything else. Seriously, fiercely, viciously. Together. The battle was long and bloody and tragic and pointless. In the end, they stood victorious, tired and empty. They were done.
So used to survival, they went through the motions for a while. Did the funerals, faces stony, expressionless, but with scarcely an inch between them, death grip on each others hands the only visible sign of the devastation raging inside. Moved in Harry's dead godfather's house. Made nice with Kreacher. Slept tangled together in a bed way too small because that's how it's always been. Hidden away from the public eye and the inevitable media frenzy. Tried to fuck each other. Failed miserably. Tried to pretend they weren't freaked out with possibly becoming asexual. Flinched at loud noises. Practised their magic through seemingly endless bouts of insomnia. Spent as much of Harry's inheritance they could on ridicculously over the top luxuries which never failed to make Harry smile faintly, and Ron and Hermione itch to crucify the Dursley's.
Trying to pretend they weren't holding themselves back from burning the world down in their anger.
Trying to pretend they weren't batshit crazy.
Really, there was a lot of lying in those post-war years, during which they left their house without a disguise less than a handful of times.
But, surviving out of inertia, out of habit, wasn't enough. Could never have been enough. They had no purpose apart from each other. No passion. No hopes or dreams. Their magic, unused to peace, was keeping them alert and always on the lookout for the next danger. Three grown-up child soldiers made by and for war. It was always going to break.
And it did. They ran out of lies, out of excuses.
They found an abandoned field, and raged and cried and laughed. Flung their chaotic magic around, let their wild emotions fly. And in the end, in a parody of an embrace they shared since they were fifteen years old, laid down in a tangle of limbs, pointed their wands at each other and with endless love cooed "Avada Kedavra".
And then they woke up.