First of all this isn't a slash story. I don't believe that the definition of soul mate is having a romantic relationship. I believe that there can be soul mates in friends and family. Some one that you love and get along with very well. If you want to think of this as a slash story go ahead. I was just stating my opinion.
I finally had time to go back and fix my mistakes so I hope that this is better.
I got this idea from MagicIf5's video 'Fili and Kili: what's a soulmate' on youtube. If you haven't watched it yet do so. It literally made me cry.
I don't own anything
Writing like this is the words from the video
Writing like this is in flashbacks.
Kili: "What's a soul mate?"
Kili laid on the ground several arrows piercing his body. He turns his head slightly to see his brother only a few inches always from him, a sword sticking out of his chest. Slowly Kili reached out a hand to push some stray hairs out of his brother's cold, dead, eyes. The battle had been terrible; certainly not like the stories Thorin had told them when they were kids. Fili and Kili had rushed to their uncle's aid after he had been over powered and struck down by several orcs. Thorin had already gone to Mahal's halls and Fili had followed shortly after. Now, Kili was the only Durin left. Kili turned his eyes toward the sky as his vision began to fade. He remembered his mother and how she had been sad for several years and would not tell him why.
"Uncle, why is mum so sad sometimes?" asked a four year old dwarfling.
Thorin looked down at his nephew, Kili. Kili had never met his father. Vili had died in battle a few weeks before Kili was born.
"Your mum is sad because it has been four years to the day that she lost your da, her soul mate," Thorin explained.
Kili was thoughtful for a few minutes before asking, "Uncle, what's a soul mate."
Thorin: "Well it's like a best friend, but more. It's the one person in the world that knows you better than anyone else."
A twenty-five year old Fili had just come home from doing chores all morning to find his brother on the floor playing with some of their toys. When Kili looked up from his playing Fili could see the hurt in his brother's eyes. Fili had learned how to read his brother's emotions at an early age and could read him like an open book. He saw the pain and sadness in his brother's eyes before he masked it with a fake smile. Kili got up of the floor and latched his arms around his brother.
"Kili, what's bothering you?" Fili asked, getting strait to the point.
"It's nothing," Kili mumbled, not wanting his brother to know about his problems.
"Kili, I know you. I'm not stupid. There is something bothering you. So, tell me what it is."
Kili sighed. There was no point in hiding it from his brother. "It just what some of the other kids at school say about me. They say I'm too small and skinny to be a real dwarf. And since I've discovered the bow, they have started to call me an elfling and a bastard saying that my da must have been an elf. Some of them go as far as ganging up on me and beating me up when there's no one else around." With that Kili started to cry, leaning into his brother. Fili was grateful that Kili was still small enough to pick up. He carried Kili to their uncle's chair that was in front of the fire place, and sat down with Kili in his lap.
"Kili, don't listen to them. You are as much as a dwarf as Uncle Thorin. You are small and skinny because you were born during a harsh winter. You would have died if it hadn't been for Uncle. And you know what, He was a winter child as well. So Uncle was small and skinny too. Besides, you are a son of Durin and that's something to be proud of. So put this behind you and let's go fix some lunch because I'm starving." This last statement brought a tinny smile to Kili's lips. As small as the smile was it was still true and not forced.
Thorin: "Someone who makes you a better person. Actually they don't make you a better person. You do that yourself because they inspire you."
Fili was Kili's inspiration. Almost everything he learned he did by watching his brother. When Fili had started learning sword play, Kili would tag along and watch and his brother learned the correct stances and positions. During his free time, Kili would then practice the stances and positions himself.
Dis had never been able to teach Kili proper behavior. Fili on the other hand only had to use his manors and Kili would try to copy his brother. Or when other dwarves Fili's age talked blasphemy about the royal family, Fili would just simply mildly threaten them before walking off. Kili always saw Fili as a perfect prince, someone to look up to and respect. Fili was his example of how he was supposed to act and behave, and was someone to inspire to be like.
Thorin: "A soul mate is someone who you carry with you forever."
"Happy Birthday, Kili!" shouted Fili as Kili came out of his bedroom that morning. "I have something for you."
"Fili you didn't have to get me anything," Kili said, trying not to yawn. Fili walked up to his brother and handed him something small that was wrapped up in a cloth. A gasp came from Kili's mouth as he unwrapped his gift to see a circle pendent with the head of a lion and a raven flying above it. The pendent was on a leather cord so that Kili could tie it around his neck.
"Thank-you, Fili. I love it!" exclaimed Kili as he tied the pendent around his neck.
"I'm glad that you do. It took me a few mouths to make the pendent and engrave those images onto it."
"You made this, Fili?"
"Yes. The lion represents me and the raven represents you. It's a symbol of our bond as brothers. I made it so that you will always have something to remind you of all the good times that we shared and will share."
Kili pulled Fili into a strong embrace before saying, "it's the best gift that you could have ever given me."
Thorin: "It's the one person who knew you and excepted you and believed in you before anyone else did or when no one else would."
It had always been difficult for Kili to fit in anywhere due to the fact that he was still skinnier than most of the other dwarflings his age. The newest obstacle was that he had chosen a bow over a sward or an ax. Bows were considered elvish weapons and cowardly. His own uncle had been against him learning how to shoot saying that, 'a prince should not relate himself to those traders'. Fili was just about the only person, besides his mother, who supported Kili in his decision. The brother's would go out hunting over the weekends when they weren't bogged down by chores or duties. Fili would use his throwing knives while Kili used his bow. Kili had become a very good hunter and almost never missed his mark, often bring home some rabbits or a deer. But no matter how many people came to except Kili's looks and choice of weapon, it had been Fili that had seen Kili's potential as a great archer and hunter when no one else did or would.
Thorin: "And no matter what happens you'll always love them. Nothing can ever change that."
Fili and Kili were almost inseparable. They may have had their good days but there were also the bad ones as well. There had been an orc attack during the night and their mother had fallen ill a few days before. Kili was left in charge of protecting his mum while his uncle and brother went out to fight. Kili had abandoned his post to rescue a dwarfling lass from being chopped in two.
"Why did you have to be so reckless, Kili? Why?! You had one job and now because of your recklessness our mum might die!" Fili yelled.
"I had no choice mum would of wanted me to save that little girl, Fili!" Kili yelled back.
"But what would have uncle wanted or da?!"
"Uncle would have wanted to protect both mum and the girl. The girl was defenseless and more of a priority than mum, because mum is able to defend herself if need be. As for da I don't care what he would have wanted because I never got to know him like you did!" With that Kili marched out of the healing halls.
A few hours later found Fili in the forest looking for his brother. Fili found Kili in one of the taller pine trees.
"Kili?" He called. "Look I'm sorry I yelled at you. You were right to follow your instincts and protect someone who was defenseless."
"It's fine Fili. I'm the one that messed up. Can you forgive me?"
"I will, only if you'll forgive me for yelling at you."
"I forgive you. And no matter what I will always love you, Nadad."
Thinking of all the ups and downs that he and his brother went through, Kili realized that what Thorin said was true. Fili had always been there for him when no one else cared. With one last effort, Kili looked back to Fili Kili whispered, "You were and are my soul mate, Nadad." With that Kili closed and aloud the darkness to take him.