A/N: For kyuumihaira. I hope this is kind of what you were looking for!
Disclaimer: Another prompt fill, blah blah, not totally my idea, blah blah.
Steve and Bucky had been best friends from the moment they met. Steve had been eight at the time, picked on by the older boys in the neighborhood because of his small size. And Bucky had charged in waving a pipe and yelling, "Don't you dare mess with my friend!"
Steve had never met this dark-haired boy before, but it had just felt right to hear him call him his friend. So when Bucky stuck his hand out with a proud smile after the bullies had been chased away, introduced himself, and invited Steve to come over and play at his house, Steve automatically accepted.
And they had been inseparable ever since.
But now it was the night before Bucky's 18th birthday and he was huddled in Bucky's bedroom, waiting for midnight. In just a few hours, Bucky would be an adult while Steve would be a teenager for another year. And more importantly, Bucky would get his soulmark.
Steve had always known one day Bucky would find his omega mate, just as Steve would find his. Still, Bucky was the only friend he had and Steve hated to think about losing him.
"Hey," Bucky said, leaning forward on the bed to clap Steve on the shoulder. His face was intensely earnest in the candlelight. "This isn't going to change things, you know. Nobody finds their soulmate in a day. So we'll get a little apartment together as soon as you turn eighteen, live together for a few years until we find our mates. And we'll always be friends, Stevie. Even after we've got families of our own. We can live right next door and have poker nights at my place and listen to the ballgame on the radio at yours. It'll be great."
Steve smiled weakly. "Sure, Buck."
Bucky looked towards the clock. "Not much longer now. How about another game of cards?"
Steve groaned, but he reached for the deck of cards anyway. Two hours passed as they munched apples Bucky had pilfered from the pantry and wagered bottle caps, shoelaces, pocket lint, apple seeds, and whatever else they could scrounge up.
Steve was sitting on a sizable winning streak of two bottle caps and an apple core when Bucky looked up at the clock.
"Midnight," he said with delight.
For a moment, nothing happened. Steve felt a rush of relief that everything could stay the same if Bucky didn't have a soulmate immediately followed by a stab of guilt for thinking such a thing.
And then Bucky cried out and clutched his shoulder. Steve stood by with a wet towel to press over the mark. Everybody said it felt like being branded, but the pain was worth it.
For a few minutes, Bucky just sat there shaking, teeth gritted against the pain. But then he took a deep, shuddering breath and gestured for Steve to unwrap the towel.
The two of them stared at the mark together. It was an eagle with two heads facing in opposite directions, wings unfurled and clutching a wrench in its talons.
Steve almost traced the outline of the mark with a finger, but stopped himself just in time. "Still hurt?" he asked.
Bucky shook his head. "Just itches now."
"What do you think it means?"
Bucky shrugged. "Damned if I know."
Soulmarks were meant to represent both mates, an amalgamation of their personalities and interests. And everyone dissected their marks for signs of what their mate would be like. But the signs weren't usually clear until you actually met your mate. Still, having a vague guide was better than nothing.
Steve carefully stroked a finger over the wrench. "Aren't you still trying to fix up that motorcycle?"
Bucky rolled his eyes. "Because my whole life can be represented by that damn bike." He shoved Steve's shoulder. "Thanks a lot, punk."
Steve grinned and shoved him back. "Anytime, jerk."
"Let's just go to bed," Bucky said. "We can come up with some better ideas in the morning." He blew out the candle and threw himself into bed.
Steve carefully slipped into bed beside him. Who knew what tomorrow would bring? This might be the very last night he spent in Bucky's bed, huddling with him for warmth. But he resolved to be happy for his friend and support him fully.
The morning dawned like any other. Steve woke up to the sounds of Bucky and his siblings fighting over breakfast and Bucky insisting that as he was a guest, they ought to save some of the bacon for Steve.
He smiled and felt a little tension in his gut subside. Things hadn't really changed after all.
True to his word, Bucky began looking for a job and an apartment where they could live together. But he was also spending more of his nights out on the town, going out with several women at a time and coming home thoroughly disappointed in the morning.
"You see what I told you?" Bucky said after nine months of failure. "Nobody finds their soulmate overnight. It takes years and years of searching. By that time, you'll be tired of living with me."
Steve didn't see that happening. His own birthday was coming up and he was frankly more excited about the idea of moving in with Bucky than searching for love. If Bucky couldn't find his soulmate easily, what chance did he have? Most people wouldn't even spare him a second glance, much less take the time for the brief body contact that would confirm whether they were mates.
Two days before Steve's birthday, he came down with a bad case of pneumonia and he was bedridden for almost a week, miserable and feverish. He only remembered his birthday when the back of his neck started stinging.
As soon as he was well enough to go out, he went straight to Bucky's house.
"I got my mark," he said cheerfully. "Back of the neck." He turned his back to his friend and tilted his head to one side so Bucky could see it better. "What's it look like?"
''Holy shit," Bucky breathed out.
"What?" Steve asked, craning his head around even though he knew he couldn't actually see the back of his own neck. "What is it?"
"Our marks are the same."
"That's impossible," Steve said. "We're both alphas."
Unless his body was even more broken than he thought.
"It's rare," Bucky said. "But I heard somebody once talking about two alphas who were such best friends they were platonic soulmates. And when they found their omega, they didn't mind sharing her."
"Co-alphas," Steve said quietly. It was the best idea he had ever heard.
"It makes sense if you think about it." Bucky pointed to his mark. "Double-headed eagle represents the two of us."
Steve grinned. "You're right, Buck." He felt almost weak with relief.
Bucky slung an arm around his shoulder. "Feels good, doesn't it? Knowing we're doing this together, just like we've done everything else. I'm with you to the end of the line, Steve. Neither of us has to ever go it alone."
Looking for an omega to share their lives with didn't seem like such a bad idea anymore.