A/N: In my headcanon Thor is older than Loki. Also this is (eventually) Bruce/Loki centric, so I apologize if I get my Thorki facts, or just Norse facts incorrect.
A few months after the whole Manhattan fiasco, war had broken out on Earth again. To Loki it felt like no time at all; it seemed he and Thor were taking hold of the Tesseract one moment and his brother was informing them of their impending departure the next. Still, there were some changes in the short time between the two events that even Loki had noticed. When the pair had first arrived upon Asgard, Thor had been cold and openly disappointed in Loki, which was punishment enough for the younger god. Not everyone agreed with him though, and he was kept in moderate isolation for some time, though it wasn't severe enough for him to be able to plan his revenge.
And while he had sat in the humble abode he was placed in, he'd thought. Was revenge really what he wanted? It had never boded well for him in the past, and he couldn't see why this time should be any different. And if the other gods saw that he was persistent in his desire to harm other races, they might not continue to be so forgiving. Thor visited him on occasion, nursing his bruised ego back to health and promising a palace to live in. By the time his sentence was over Loki had more-or-less decided not to go into action, at least not for some time.
When he returned to live with Thor, his brother seemed cautious of him, making Loki even more wary of executing any unexpected actions. Though time passed quickly for the brothers, Loki made sure to make every second count around Thor. He had to prove that he could be good and that he deserved Thor's admiration, which the elder god seemed to pass around so freely.
By the time Thor felt the call to action Loki was in his good books again, helped along by some less-than-brotherly persuasion. Those activities were not something either of them were likely to ever to admit to, but Thor assured Loki that it did not surpass any boundaries that he had. Thor liked to think that love was simply love, and Loki cherished his brother because of it. When it was time for the pair to ascend to Earth their bonds, both physical and emotional, were very strong and Loki very rarely wanted for more. Sometimes he wished for someone he could be more open with, someone he could relax with and not have to worry about if anyone saw them together. It was on one of these particular days that Thor visited him in his chambers.
"Brother?" Thor's voice rumbled through the room Loki had been sitting in, playing a human game called Chess with a copy of himself so he could see the game from both sides.
"Yes?" The slight god did not bother to look up from his game.
"May you return to your normal state? We have much to discuss and little time to do so." Loki rolled his eyes but complied, turning to face Thor from behind the array of black and white pieces littering the board. He had taken to playing the white side, a metaphor which never failed to amuse him. To think I've become soft like this. When Loki had first learned to play Chess he'd been taught that while white went first, black were the true mercenaries as they had to know how to work their disadvantage.
"What is it?"
"We must return to Earth." Loki stiffened in his chair. He'd been expecting Thor to return to the dreaded planet, but he'd thought he would have more time.
"When will you go?" He felt that he did not need to know the specifics; Thor would leave, and he would eventually return, perhaps with someone new on his extremely muscular arm.
"I fear you misunderstand. You are to come with me, we need your knowledge and powers now more than ever."
"And what if I do not wish to return?"
"Then you shall remember the great debt you owe the humans, and me." The conversation seemed to end with Thor's statement, but Loki continued to glare harshly at his brother, blue eyes flashing. Eventually he relented.
"Why are we doing this?" Thor shrugged.
"I do not know, exactly. The... Avengers need help, someone else has attacked them and the man in the iron suit can only do so much."
"I do not believe his uniform is actually made out of... never mind. When shall we go?"
"Now, unless you have something better to attend to."
"I do not."
"Good." Thor held his gaze again before sweeping in and kissing him softly. Loki's body quickly replied to the kiss, pressing in and practically begging for more. A small sigh escaped his lips when Thor pulled back. "There will be more of where that came from when this war is won."
And after that it had been a relative blur to Loki. Thor had figured out some method of transportation so the Tesseract would not be disturbed, and Loki had once again been thrust into close proximity with a number of people he had planned on never seeing again. He had stayed in his own little corner, messing around with one of Stark's computers while everyone else drew up a battle plan. He was not allowed to help with such activities, and while normally this would have irritated him he found himself quite indifferent to the matter. Their little blueprints were nothing to what he had stored in his mind anyway.
So he'd been sulking and messing around with needless information when a figure had drifted over to him. At first he'd pretended not to notice, acted like he was in his own little world so the person would think he was boring or perhaps insane and leave him alone. Of course he had no such luck, and the human, or not, he thought to himself, plopped down next to him rather unceremoniously.
"Can I be of your service somehow?" He'd always had trouble with idioms, never feeling the need to sugar coat or 'slangify' what he was trying to say.
"What'cha working on?" The man asked nervously.
"Absolutely nothing. Do you need this?" Loki held out the tablet for the man to take.
"Uh, be careful with that. No, I just..." He paused, running his hand through his hair and squinting sheepishly. "I'm pretty crappy at coming up with game plans. I prefer to be behind the scenes. You know, in a lab."
"How wonderful for you." The man seemed unparalleled in his desire to keep their conversation going. Loki saw Thor smirking in his peripheral vision.
"Uh, yeah. I'm Bruce, by the way."
"Yes, I know. We've... met before." Under tragically unfortunate circumstances, in Loki's opinion. 'Bruce', or as Loki had known him, the Hulk, had been a major reason for Loki's failure to take over Manhattan and on a larger scale, the Earth.
"I'm real sorry about that. The 'other guy' doesn't really think things through."
"It was necessary." Loki conceded. Where would he be now if he had been successful? Probably dead, thrown aside by the ones who had used his emotions to turn him into an evil war criminal. Bruce nodded shortly in agreement.
"Banner, I need your help on this. Think we can manage a mini-A-bomb?" Bruce turned to the voice that was calling him from across the room.
"Be there in a minute, Stark." He looked at Loki for a minute, deciding if he should attempt to touch him in a friendly way or just walk away. He chose not to push the god's boundaries. "It was... nice to talk to you."
Loki shrugged in response, turning back to the tablet and opening Galaga, a file which had somehow been stored on the computer's server despite its apparent lack of purpose. He quickly became immersed in the game and entirely missed the second person who walked up to him until their shadow shrouded him entirely.
"Enjoying yourself, brother?" Loki jumped at the low voice and resolved to not let himself get so distracted again. Galaga could certainly be used as a very strong weapon. He chose to ignore the question and instead find out what they were to do next.
"I take it the plans are finished?"
"More or less. There are some technical things we need not worry about. We have one night to achieve full strength and then we must be ready for battle. There are rooms for us in the upper level." And that was that. Loki followed Thor up to their suite and made him -albeit rather willingly on Thor's part- give up his promise to wait until the fight was over to indulge himself in his brother.
When they were both relaxing after the fact, Loki let his fingertips trail over Thor's chest. He reveled in the way his brother shivered at his touch, how the littlest things could break the strongest of gods.
"Are you so eager for more?" Thor asked jokingly.
"Not at this time. I fear I will not be able to properly sit down tomorrow, or the day after." Thor smirked knowingly, safe in the well-established knowledge that he could never really hurt Loki unless he was trying.
"Then perhaps you should cease acting so teasingly." Loki chuckled to himself before letting Thor wrap his arms around him and nestling into the larger god's embrace.
The fight passed quickly; it was really more of a skirmish and Loki was scarcely needed. It seemed that the threat had been greatly exaggerated. As much as he largely disliked the idea at first, Loki found himself spending a fair amount of time with Bruce, who he'd resolved to call Doctor Banner. It was better than 'that evil mutt who ruined my plan', or so Thor said. The older god encouraged their relations, which Loki first suspected was because he'd found someone else but later realized was because Thor simply wanted him to be happy.
The two had never laid any guidelines for their relationship; Thor being too stereotypically a human male and shying away from the topic while Loki was too much of a nitpicker to sit with one label. It wasn't like he'd ever be able to say "This is Thor, my-" anyways. They couldn't really go anywhere where no one would know them, not without severing all ties with Asgard. And though Loki loved Thor, he wasn't sure that what they had was worth it. Perhaps, he sometimes thought to himself, that is why he did not interfere. Perhaps that is why he encouraged me to make amends with the others. So I would find someone worth fighting for, and worth running away for. What a shame for him that I succeeded.
When everything was over and the destruction was nearly cleared up, and it was obvious that Loki was not going to try to take over the world again, Thor made an announcement. Over one of the last Avengers dinners, at least until the impending Next Time, he declared that he would be spending some more time on Earth. He wanted to work on helping the planet build their defenses so matters such as coming all the way from Asgard would not be recurring issues. One day, he said, Earth would have to defend itself, and possibly even help out the Asgardians.
Loki warily agreed to stay on the blue planet for the time being, knowing that life would be no better on Asgard. At least on Earth there were amusing humans, even if he couldn't torment them physically. As their time on Earth stretched from hours to days, to weeks, Loki felt his relationship with Thor diminishing. They were still closer than most brothers and he knew where to go if he ever needed a release, but what once were throes of passion turned simply to lust and a way to get rid of frustration. On a particularly bleak and rainy day Loki decided to end their tryst.
Thor had just entered the suite they were still 'borrowing' from Tony, who Loki had also somehow found himself acquainted with in a not entirely unpleasant way. The tall god trudged into the room, picking up a towel to dry his sopping locks with. Loki looked up from the window he had been staring out of and turned to face his brother. He felt especially naked confronting a problem without his battle uniform, but had taken to wearing modern human clothes so he did not feel trapped inside or judged when he went out.
"I believe we should talk." He said quietly, not approaching Thor. Thor smiled sadly, expecting what was coming next.
"So soon?" Loki nodded. "I did not expect you and Doctor Banner to, how is it the humans say? Go steady, quite so early in your relationship."
"He has nothing to do with it." Loki stated plainly. It was true, too. Just as he wouldn't have an emotional relationship with another person while he was with Thor, he would not enter into a relationship with Bruce if he could not give all of himself. The two had remained friends amidst immense sexual tension. "I simply feel that what we have has… run its course. I will continue to love you as long as my heart permits, for it knows no different, but I cannot lie to you or myself."
"Can I have you, one last time?" Loki nodded his assent and they silently began disrobing each other in a much-practiced way. When they were finished Loki laid in his brother's arms for what could possibly have been the last time and pressed soft kisses wherever he could reach. "I love you." Thor whispered.
"I know."