Posted originally on the Archive_of_Our_Own at https://archiveofourown.org/
works/8143889.
  Rating:
      Explicit
  Archive Warning:
      Underage
  Category:
      M/M
  Fandom:
      Teen_Wolf_(TV)
  Relationship:
      Derek_Hale/Stiles_Stilinski
  Character:
      Derek_Hale, Stiles_Stilinski, Scott_McCall, Alan_Deaton, Sheriff
      Stilinski
  Additional Tags:
      Unexpected_Relationship, Soul_Bond, Soulmates, True_Mates, Mating, Mating
      Bond, Mating_Bites, Knotting, Alpha/Beta/Omega_Dynamics, alpha!Derek,
      Human!Stiles, Stiles_Stilinski_Gets_Bitten, Only_slightly_underage,
      Stiles_is_17
  Series:
      Part 1 of Unexpected_Mates
  Stats:
      Published: 2016-09-26 Words: 3862
****** Unexpected Mates ******
by Kleineganz
Summary
     Derek scents Stiles when they were paralyzed together at the
     Sheriff's office, and it sets in motion something in their biology
     that they cannot control.
Notes
     This is my 32nd fan fiction work, but my first in the Teen Wolf
     fandom. I hope I captured their voices well enough (let me know if
     anything seems ridiculously out of character). I'm sure similar
     stories to this exist but this is my take on it. I hope people enjoy
     it!
See the end of the work for more notes
Derek lay paralyzed on the floor of the Sherrif’s office as Stiles made a
snarky remark to Matt. Seconds later Jackson, half-transformed into a Kanima,
attacked and Stiles tumbled on top of him, landing like a dead weight.
“Get him off of me!” Derek growled, slightly breathless. Matt teased at what a
“pretty good pair” they made, and Derek held back a growl at the very thought,
trying to keep flushing with embarrassment when part of his brain agreed. Once
Derek is able to draw in a deeper breath, that’s when he noticed it. Stile’s
scent, under the mix of fear and uncertainty. Mate.
Then suddenly Stiles is being pulled off him and Matt is threatening Stile’s
life with a foot on his trachea and Derek internally panics. His mate is in
danger and he can’t even move to save him.
Wait, no. Mate? Stiles can’t be his mate. That’s impossible. Stiles is human.
Sure, weres can have sex with humans, but mates? No, the mating bond only
happens between two weres.
Later as they lay next to each other, still paralyzed, Derek can feel the heat
coming off Stiles. He still smells the human’s fear, but beneath it all, there
is still the unmistakable scent of mate. Derek tried to put it out of his mind.
Instead, he focused on trying to break the paralysis by kick-starting his
body’s natural healing, while he explained to Stiles about how Matt is breaking
the rules of the Kanima.
***
Everything finally came to a head, with Jackson cured of the Kanima curse and
fully transformed into the werewolf he had longed to become. Gerard Argent was
poisoned with mountain ash and eliminated as a threat after he was bitten.
Finally, they had some peace and quiet.
After it was all over, Derek stayed as far away from Stiles as he could, as the
boy finished out the school year with his friends. The last thing the human
needed was a werewolf trying to mate with him. Unfortunately, Derek couldn’t
stop thinking about him and he became increasingly agitated the longer he
stayed away from Stiles.
Desperate, Derek finally made his way into town, to pay a visit the veterinary
clinic. When he arrived just before closing he was slick with sweat and
breathing heavily. Dr. Deaton came out from the back when he heard the front
door open and looked shocked to see the were. “Alan, please help me,” Derek
pleaded.
Alan closed the clinic and ushered Derek into the back. Derek explained as best
as he could. “Why is this happening? How can a human be my mate?”
Alan was silent for a moment. “This is very rare, and I haven’t heard of a case
of this in my lifetime.”
“What? What is it?” Derek pleaded.
“Stiles may still be human, but it seems he’s destined to be your mate,” Alan
explained. “When you came in such close contact with him, with his scent and
pheromones, it started the process in you. Your body knows that you’ve met your
true mate, and now it has a need to claim. If you don’t, you could die.”
“I’ll die if I don’t claim Stiles as my mate?” Derek growled. “Stiles?
Really?!”
“I’m afraid so,” Alan confirmed. “There’s no cure for this either. Stiles was
born to mate with an Alpha. He must also be suffering at this point as well,
and as a human, the likelihood of it being fatal is almost guaranteed. When is
the last time you saw him?”
Derek shook his head, trying to recall the last time he had seen the lanky
teen. “The night we killed the Kanima. When Jackson finally became a werewolf,”
Derek recalled. “I’ve been avoiding Stiles since then.”
***
Stiles was in bed, groaning in pain. His entire body was slicked with sweat and
he felt hot and fevered. His dad wasn’t home yet and he wasn’t sure if he
needed a doctor but Stiles was pretty sure he was sick.
All of a sudden Scott burst in, a cell phone pressed to his ear. “Yeah, Dr.
Deaton, Stiles is here.”
“Uhnnn, Scott, what’ya doin’ here?” Stiles mumbled as Scott reached out to feel
his sweaty, fevered brow. “Yeah, he’s burning up! Should I call an ambulance?
Uh-huh. Okay. You’re sure? Well, alright, but get here quick.”
Scott put his phone away and came over to lift Stiles out of bed. “Dude, I’m
sorry, but Dr. Deaton said to make you take a shower to cool you down. He and
Derek are going to be here soon.”
“Derek? Why’s Derek comin’?” Stiles asked.
Scott shook his head. “I dunno. Dr. Deaton said something about only Derek
being able to help you now.”
Scott carried Stiles into the bathroom and stripped them both down to just
their underwear before helping his friend into the shower, turning the water on
and leaving it at a cool temperature. Scott got in behind him and helped Stiles
to remain standing. He shivered slightly as the cool water hit his skin. “Stay
with me, buddy.”
***
Alan and Derek arrived at the Stilinski house and Derek was relieved to see
that the Sheriff was not currently at home. This entire situation was going to
be awkward enough without having to try and explain it to Stiles’ father.
Derek led Alan up to Stiles’ bedroom and they could hear the shower still
running. “Scott? Stiles? We’re here!”
Derek ran into the bathroom just as Scott was turning off the water and he
grabbed a towel to wrap Stiles in, lifting the fevered boy in his arms and
carrying him back to the bed. Derek noticed that he immediately began to feel
better as soon as Stiles was in his arms. Alan began to check Stiles over.
“He’s in heat, which is dangerous while he remains human.”
“Wait, what?!” Scott cried out. “What do you mean remains human?”
“Look, there’s no easy way to say this,” Alan sighed. “As I was telling Derek,
this is a very rare occurrence, where a human is born with the genetic
compatibility to become the mate of an Alpha. When they both were close enough
to scent each other a couple of months back, it kicked off the process and
Stiles’ body has been changing for him to take on his role as Derek’s mate.”
Stiles seemed to come back to himself a little at Derek sat close to him and
his eyes went wide when Alan said the word mate. “Wait, my role as what?”
“I’m sorry Stiles, but you and Derek must have sex, or I’m afraid you will both
die,” Alan explained. “Human bodies are not designed to go into heat like this,
and the death of a true mate can kill an Alpha as surely as a wolfsbane bullet
can. Derek must claim and mate you, and thereby turn you as well.”
“I’m so sorry Stiles,” Derek apologized. “I…wish it didn’t have to be like
this.”
“Isn’t there another way?” Scott asked, clearly distressed for his friend.
Alan shook his head. “I’m afraid not. Stiles and Derek were literally born for
this,” Alan said. “It’s part of his genetic makeup. It’s extremely rare. This
wouldn’t have happened unless they were uniquely compatible with each other.”
“So when you say we have to…have sex,” Stiles asked. “Is that it? Does that
cure us?”
“No,” Alan said. “You will become bonded for life.”
“Derek has to bond himself to me for life?” Stiles was incredulous before he
started to giggle. “You don’t even like me and now you’re stuck with me? I
guess there’s some poetic justice in that.”
Derek looked at him then, his eyes burning into him with a passionate
intensity. “You’re wrong about that,” Derek said quietly. “I actually do like
you. More than I should. I’m dangerous, everyone around me gets hurt. That’s
why I was always pushing you away.”
“Oh,” Stiles blushed. “And now?”
“And now, either I let you into my life or you die,” Derek said with a hitch in
his throat as he reached out and cupped the side of Stile’s face. “I don’t want
you to die. Especially if there is something I can do to save you.”
Stiles leaned into the touch as he looked up into the Alpha’s eyes and saw the
sincerity there. Just then they heard the Sherrif’s car drive up. “Shit, my
dad’s home!”
Quickly they got Stiles and Scott dressed and Derek hid in Stile’s closet, so
that when Sheriff Stilinski came in to check on his son, he found Scott and
Alan sitting next to Stiles with several textbooks strewn around the bed.
“Hey, Dad!” Stiles said nervously. “How was work?”
“It was fine,” the Sheriff said suspiciously. “What’s going on here?”
“I’m just helping the boys out with some of their biology homework,” Alan
explained.
“Yeah,” Stiles nodded. “We’re almost done. Scott and I were thinking of going
out afterward, I might sleep over at Scott’s tonight if that’s okay? There are
leftovers in the fridge for you.”
“Alright,” the Sherriff said, still looking slightly suspicious. “Thanks for
helping the boys out, Alan.”
***
A half-hour later found them at Derek’s new apartment. He’d just moved in a few
days before, after he realized that he couldn’t keep living at the burnt out
remains of his family home indefinitely. Derek was carrying Stiles bridal style
over the threshold and Derek growled at his soon-to-be mate in warning.
“Ok, ok, not going to make a bridal joke,” Stiles giggled.
Alan and Scott had accompanied them but now all Derek wanted was some privacy.
He knew what had to be done and he didn’t want an audience. As he lay Stiles
onto his bed, he turned to Alan and Scott. “I think I can handle it from here.”
“Yeah, I know,” Alan said. “I just want to hear it from Stiles. Kid are you
okay with this?”
“What choice do I have? It’s either this or death, right?” Stiles replied. “But
yeah, I’m okay with it…with the mating part anyway. Hey, I finally get to lose
my v-card!”
Stiles laughed and then turned quiet for a moment. “The part…the only part
that’s bothering me is needing to be turned.”
“I’m sorry, but it’s necessary,” Alan explained. “If you don’t turn, whenever
you go into heat, if Derek isn’t close by, you could die. Your body isn’t
designed for it. As a were you’ll still be in distress, but there will be no
threat to your life.”
Stiles nodded. “Got it. Alright then. Time to add me to your pack then, Alpha.”
Satisfied, Alan and Scott retreated. “I will be by tomorrow to check on you
both.”
***
Derek stared at Stiles as he heard his door clang shut. He flicked his eyes
over the boy’s youthful features, remembering how young Stiles was.
For a moment they just stared at each other before Derek growled and got up to
pace. “This is so frustrating. This isn’t…I never…”
“I know,” Stiles said. “But yet, here we are. So c’mon…save my life already.
Whenever you’re away from me I can feel this heat start to build up again.”
Derek nodded and made his way back to the bed. “For what it’s worth, I’m sorry
you’ll never get to be with Lydia now.”
Stiles left out a puff of laughter. “Dude, I was never going to be with Lydia.
I knew that, but it was fun to dream.”
Derek crawled up over Stiles then, reaching out to cup the boy’s face,
marveling at the smoothness of his skin. He lowered his head to brush his lips
against Stiles’, taking in his mate’s scent. This time there was no smell of
fear overlaying it. All Derek could smell was a mix of arousal, uncertainty and
mate.
Derek deepened the kiss, sliding his tongue into Stiles’ mouth as he slowly
lowered his body, so that Stiles could feel his growing arousal against his
hip. Derek was pleased to feel Stiles’ arousal as well, as the boy arched into
his touch.
Derek knelt above Stiles and frowned. “I don’t want you to freak out, but I
almost forgot. When I claim you, I have to do it in my werewolf form. There are
a couple of things you’re going to need to know about having sex with a
werewolf, especially when a claiming and mating bond are involved.”
“Ok,” Stiles gulped. “Since I know I’m going to have to be turned, that
involves biting, right?”
“Yeah,” Derek acknowledged. “Specifically I’m going to have to bite you here,”
Derek said as he caressed the juncture of Stiles neck and shoulder on his right
side. “Hold still when I do it, I don’t want to hurt you any more than I have
to.”
Stiles gulped and nodded. “What else is there?”
“When I’m aroused in my were form, I develop a knot,” Derek started to explain.
“Much like a wolf or a dog. To successfully mate, I have to tie you with my
knot. That part is probably going to be as painful as the bite.”
“How…how long will we remain tied?” Stiles asked.
“I’m not sure,” Derek shrugged. “I’ve never knotted a lover before. Knotting is
only for mates.”
Derek could hear Stiles' heartbeat and it seemed to speed up a bit every time
he said the word mate. “Let’s get you out of these clothes first,” Derek
suggested as he began to pull Stiles’ t-shirt up. The boy lifted his arms
obediently and let Derek remove it.
The Alpha then climbed off Stiles and helped him remove his jeans and
underwear, noting how Stiles blushed a deep red when his arousal was exposed.
Derek removed all of his own clothing as well before lying back down next to
Stiles. “You’re beautiful,” Derek breathed as he captured the Stiles’ mouth
again, kissing him breathless while running his hands over every bit of heated
skin he could touch.
Stiles was a little more nervous now and Derek continued to caress him, pulling
him closer so their erections could slide together. Stiles groaned at the
contact and Derek began to kiss and lick along Stiles’ neck, sucking the skin
and breathing in Stiles’ scent. Stiles seemed to instinctually arch his neck to
give the Alpha better access. “Mmm good boy,” Derek praised as he continued to
kiss and suck Stiles’ skin.
Once Stiles was completely boneless in his arms, Derek pulled back to look into
the boy’s lust blown eyes. After kissing his lips thoroughly one more time
Derek pulled back and reached for the table next to the bed to grab the bottle
of lube that sat there.
“Get on your hands and knees for me sweetheart,” Derek instructed. “I need to
prep you first. I don’t want any of this to hurt any more than necessary.”
Stiles shifted and got onto his hands and knees, burying his face in his arms.
A mix of arousal and embarrassment was coming off of Stiles in waves now and
Derek chuckled as he coated his fingers with lube and began to slowly caress
Stiles’ anus. The boy moaned at the touch. “Have you ever touched yourself back
here?” Derek queried as he slowly began to work a finger into the tight
sphincter.
Stiles shook his head. “No…no I haven’t. I never thought I’d…be doing this.”
Derek stroked his other hand soothingly up and down Stiles’ thigh as he kept
working one finger in and out of the boy’s hole. “Always thought you’d hook up
with a girl, right?”
“Yeah,” Stiles started to chuckle, but it turned into a loan moan as Derek’s
finger was fully inserted inside him now. “Oh fuck that feels…weird. Good
weird, but still…weird.”
Derek began to slowly slide his finger in and out as he crooked it and shifted
until he found Stiles’ prostate. When he began to purposely rub along that, the
boy arched into his touch. “Oh fuck…fuck…shit that feels amazing!”
“That, sweetheart, is your prostate. It’s the male g-spot,” Derek explained as
he continued to stimulate Stiles, spiking the boy’s arousal. “I’m going to put
two fingers in now. Try and relax for me.”
Stiles did his best to relax as the second finger breached him and he felt the
burn of the stretch. The burn eventually faded into a feeling of pure pleasure
and as soon as Derek sensed that, he added a third finger, and eventually a
fourth. Stiles was going to get his virgin ass knotted on an Alpha cock tonight
and he needed all the preparation he could get.
Soon Stiles was moaning and writhing, pushing back into Derek’s thrusting
fingers.
“Alright, I think you’re ready for me,” Derek said. “I’m going to fuck you now.
I’ll stay human as long as possible, okay?”
Stiles just moaned incoherently and Derek chuckled again as he slicked up his
length and poised himself at the boy’s entrance, holding his hips firmly. “I
never thought I’d get to do this. You do have such a beautiful ass,
sweetheart.”
Derek slowly began to slide his cock into Stiles’ stretched hole. Every time
Stiles clenched Derek would stop and allow the boy time to adjust. Even with
all the prep, Derek’s human cock was quite large, and it would only get larger
once he transformed.
Finally, Derek was fully inside Stiles. “You feel amazing baby,” Derek moaned,
bending over to pepper Stiles’ back with kisses. “You’re taking me so well.
Your virgin ass is so tight.”
“M’not a virgin anymore,” Stiles groaned, with a smile on his face.
Derek began to slowly slide in and out and he chuckled again. “No baby. You’re
not a virgin anymore.”
Derek rose up and gripped Stiles’ hips firmly as he began to thrust harder.
“Fuck, sweetheart, I’m not going to last long. I have to transform soon.”
“Ok, ‘m ready,” Stiles mumbled as he continued to moan in pleasure. “Feels so
good D’rek.”
“Remember, when I transform, my dick is going to get bigger,” Derek reminded
Stiles as he continued to rut inside the teen.
Derek was close and he couldn’t wait any longer, so he slowed his thrusting and
allowed his wolf to come to the fore as he lett the transformation take hold.
Stiles keened as the cock inside of him slowly grew in length and girth. Derek
growled but still had enough wherewithal to add more lube before he leaned
forward. Derek placed his clawed hands on the bed on either side of Stiles’
shoulders and began to tentatively lick the spot he would soon bite to place
the mating mark.
Stiles bared his neck for the wolf, knowing what had to happen and Derek
growled his approval of the submissive gesture. Then, Derek began to thrust in
earnest, rabbiting in and out of Stiles like the wild beast that he now was.
His knot had already begun to form and was catching on Stiles’ sore and
stretched hole.
“Relax,” Derek growled, his voice deep and rough. “I’m going to knot you now.”
Derek began to pound into the boy until his knot finally slipped past that
tight outer ring of muscle and tied them together, causing Stiles to cry out.
Once the knot was fully inside, Derek continued to thrust shallowly, dragging
his knot across Stiles’ prostate. “Cum for me, cum on my knot,” Derek ordered.
Stiles was pushing his hips back, angling them trying to get the right friction
against his prostate. He was close, so close. Derek could smell it on him. It
took several more thrusts against his prostate and then Stiles cried out,
cumming untouched, and shuddering beneath Derek’s onslaught.
Derek kissed the spot he was about to bite, praising his mate. “That’s perfect
baby. You’re so perfect for me.” Then Derek growled out his own release just
before he sank his fangs into Stile’s neck, just holding his mate there with
his teeth as he began to release copious amounts of cum inside Stiles, his own
senses whiting out at the onslaught of pleasure.
Once Derek came back to himself and released Stiles from his fangs, Stiles was
whimpering. The werewolf gently maneuvered them so that they both lay on their
sides, still tied together.
Stiles drifted on a wave of euphoria for a while after that, feeling safe and
secure in his Alpha’s arms. He woke up sometime later with Derek gently licking
the mating mark. “Did it…work?” Stiles asked groggily. “Why hasn’t the bite
healed?”
“Yeah, it worked,” Derek growled, still transformed. “You already smell more
like a were, my sweet mate. It’s the bite of an Alpha so it just takes longer
to heal.”
Stiles snuggled closer to Derek. “I don’t know why, but I love hearing you call
me mate,” Stiles said, and he felt how pleased Derek was to hear that. “Wait
why am I feeling that?”
“It’s the bond sweetheart,” Derek explained. “Were bonded together now, for
life. The bond allows us to sense each other better. It should grow stronger
with time.” Derek was flooded with the sense of happiness and security that
Stiles felt then and he hugged his mate a little tighter.
They both dozed again and when they woke up next, Derek’s cock had slid out of
Stiles and he had transformed back into his human form.
Stiles turned and looked at Derek, studying his mate’s face, reaching out to
stroke and caress the smooth skin and rough stubble. The feelings of love and
caring that flowed between them now was so strong it brought tears to the boy’s
eyes.
Derek blinked as he began to wake. “Hey, don’t cry,” Derek cooed as he reached
out to pull Stiles into an embrace. “I know it’s all a bit overwhelming at
first.”
Stiles nodded as he ducked his head under Derek’s chin. “I…just can’t believe
it. You love me, don’t you?”
“Yeah, I do baby,” Derek confessed. “I have for a while now.”
“Why didn’t you ever say anything?” Stiles asked.
“Would you have believed me?” Derek replied.
Stiles thought about it chuckled. “No, I guess not.”
Derek pulled back so he could look Stiles in the face. “I love you, Stiles
Stilinski,” the Alpha said with all sincerity.
Stiles felt it so strongly and he realized he was very quickly falling for
Derek. “Yeah, I think I’m gonna fall for you hard.”
“I hope so,” Derek teased. “We’re mated for life now, kiddo.”
“Shit,” Stiles said as he came to a realization. “How are we going to tell my
dad?”
Derek groaned. “I think we’ll need Alan to help explain it all to him, but I
think until you turn 18 next year you have to keep living with your dad. Let’s
make a show of a slow courtship so that by next year maybe he’ll accept you
moving in with me.”
“Yeah,” Stiles smiled. “That sounds like a good plan. It’s going to take him at
least that long to warm up to the idea that I’m not just dating a guy, but big,
bad Derek Hale.”
End Notes
     I'd love to read comments from people letting me know what you
     thought of this one-shot.
Please drop_by_the_archive_and_comment to let the author know if you enjoyed
their work!