Stiles is aware from the moment that the pack have moved into Derek’s newly renovated childhood home that something is going on. Stiles might not be a werewolf but he can still smell and sometimes it isn't Erica who walks through the door even though it is her scent that's coming. Rosy and wild. It's Isaac instead. There are lacrosse gear laying in Erica’s room more often than not and he walks into Isaacs’s room to bug him about dishes he hasn't done but he is seldom there. He is noticing that Isaac has become more and more open to touches and now days often lean in to hug people or just put a hand on their shoulders without thinking about it. It's nice, Stiles thinks, but he is totally certain it hasn't just to do with the fact that the pack now live together.
When he walks into Erica’s room one day, without knocking because that is just what he does, she isn't alone. They're standing close together by the window just in front of the door and when Stiles can see the tears on Isaac’s face he suddenly doesn't remember what he's doing there. Erica gets a possessive look on her face and pushes Isaac behind her as the blonde boy turns his head away from Stiles, wiping at his face.
“You think you own this place and can just barge in, dumbass?” Erica growls and Stiles know that the Betas have a hard time seeing him as “Stiles, second in command” because he's human and he's Stiles and he does dumb shit like walking into people's personal rooms without announcing himself. That doesn’t really send the most “I show you respect, so you show me respect”-vibe as he would like. So he doesn't give her a hard time, he simply excuses himself and leaves before it gets (more) awkward.
Erica is making snarky remarks about him all afternoon, it gets so much that Derek raises a brow at her and then she finally stops. He looks at Stiles who just waves a hand like “it's really nothing”. He can see that Derek doesn't believe him but doesn't push it further.
Now when he is looking a bit closer, he can see that Erica and Isaac practically always are close. They sit next to each other at all their shared meals, they help one another with homework, they steal touches, they share glances. He feels happy for them. They are cute together and he has never seen either of them smile like they do at each other when the other one isn’t watching. It doesn't seem to be official, but he thinks the rest of the pack is highly aware. Even Allison and Lydia must be, the girls have been having so much bonding time lately that there is just no way Erica hasn't told them like everything. Sometimes Stiles wishes they could just include him in these girl talks so that he can find out more about them, but he is firmly denied.
“You’re a guy,” Lydia tells him.
“It’s not that we don’t like you,” Allison says. He rolls his eyes at them.
Things turn for the worse some time later. Stiles is sleeping over, everyone is actually there, even Scott and Allison and Lydia, the ones who are not living there permanently because it has been a day of fighting off evil fucking witches. And it’s a Saturday so everyone just fell asleep around the living room after their three o’clock pizza rolls and pack snuggles. He wakes, mouth dry and looks at his phone to know that it is six in the morning. He couldn't have gotten a couple more hours? He scrambles to his feet to get a glass of water as quiet as he can and jumps over piles of humans and werewolves on the floor. Doesn't register that there are a few missing. So when he enters the kitchen, he’s shocked to find himself not alone. Also the fact that the two wolves seem to be highly unaware of his presence is rather shocking. They should smell him, Axe and sweat, hear him, heartbeats and breathing. They don’t. One of them is Erica, hair intertwined in the other wolf's fingers, pulling and smoothing. The other one is not Isaac. But they’re kissing. She has fevered lips on her own, on her neck, on her cheeks. Her eyes closed but she is smiling. And Jackson is smiling into the nape of her neck as he bites her playfully. Stiles cannot wrap his head around the fact that they are kissing. And not just any kind of kissing, because holy shit, that is so not PG 13. They must be so caught up in each other since none of them acknowledge the fact that Stiles is right there, so he backs away and leaves them to it. He doesn't understand what it all means. Is Erica dating them both? Or isn't she dating Isaac at all? He had just thought since they were always… Maybe they weren't because how would neither Isaac nor Jackson smell Erica on the other wolf? Or maybe she's not exactly dating Jackson? He resorts into thinking that Erica might have broken up with Isaac and this is the first time she’s ever been with Jackson. He almost trips over Boyd when he walks back into the den and then he tries not to visualize the wolves in the kitchen when he lays himself in a sandwich between Derek and Scott. It’s damn hard, because even though he can’t hear them, he knows things are going down.
He walks around for a week not knowing what to do. He inspects. Erica is still spending time with Isaac and being all couple-y - except Stiles realizes they never really do anything couple-y. They don’t hold hands, if you don’t count a second or two every other day, they don’t kiss and they don’t really hug an over excessive amount either. Erica seem to have exactly the same type of relationship with Jackson. Heart-eyes and the whole nine yards and Stiles is just dumb found. What is even going on? He wishes he could ask them, but there is noooo way he’s stepping into that kind of territory without having supernatural powers to count on, fact is that they would probably bite his neck off if he did, being Derek’s second or not. He sees all three of them spending time together at times, cooking or washing dishes, but it’s mostly in the presence of the others in the pack too and Stiles always gets too distracted by Derek in the end to register any type of weird behavior between them.
It turns out Stiles have not looked closely enough. Erica is sure dating both Isaac (Stiles has now had the absolute pleasure of seeing them stealing kisses when cleaning after a pack meeting) AND Jackson (he can smell Jackson all over Erica, even though Stiles almost smells like him just by being in the same room as the guy (he should really drag down on the amount of perfume he's wearing), too many times for it to be a coincidence). What he didn't see before, was that both of the guys are fully aware of this fact and doesn't even seem to mind. It makes Stiles wonder if they are not so very serious, that it’s just dating and hooking up for fun, but he eventually drops that idea too. Most of the times, it just seems like Erica is in love with the both of them and they are in love with her. He realizes that okay, Erica always sits next to Isaac on meetings and dinners but Jackson does always sit next to Isaac as well and there are usually two lacrosse sticks in Erica’s room, not just one and Stiles is just amazed on how much he hasn’t seen this. And then there are all these small gestures the three of them do, like giving each other pep talks, brush a hand over the small of each others backs, the kind of loving banter you just don’t have with friends or family and Stiles may be a bit jealous. He has Derek, he knows he does, he knows that Derek is his when the time is right. He isn’t eighteen yet so Derek has promptly said that “No, nothing will happen, Stiles, if this is “meant to be” as you say, we can wait a few months”.
When Stiles realizes he’s missed yet another point in the relationship between his three pack members, he wonders whether his gaydar is malfunctioning. Because all of a sudden there are just so much touching going on between Isaac and Jackson and it hasn't even increased. Stiles is just now noticing it, he hasn't been looking for it so therefore he hasn't seen it. They aren’t making the same kind of heart eyes at each other as they do towards Erica, but they are making eyes at each other, fucking bedroom eyes. It’s a bit too much for Stiles’s brain and he has to tell Derek. So he does. And Derek laughs at him. Stiles tells him not to laugh, it’s true, three of his Betas are in a relationship and it looks to Stiles like they really are ALL three. Derek nods his head.
“I know, Stiles,” he says lightly.
“You know?” Stiles is baffled. Derek nods.
“They all sleep in the same bed and their scents have been mingling together for more than pack goes for a while now. Have you even seen them around each other in the last couple of months?” Stiles is pacing the room because he have been seeing them around each other but still been oblivious. He wonders whether the rest of the pack already knows and he’s the last one to realize things. He most be looking in much distraught because Derek’s voice is final when he says:
“It's not a big deal, Stiles.” And at first when he says it, Stiles wants to protest because how the hell can it not be a big deal?! But the more he thinks about it, the less of a deal it becomes. It’s just… love. Derek can probably see his mind changing and adds pointedly, just to be sure Stiles gets the point:
“It's their relationship and what they do with it totally up to them and if they want to talk to any of us about it they will.” He has had this conversation with Stiles before. About their own non-fucking-existing relationship. Derek isn't much for talking about his feelings so they haven't told the rest of the pack of their pact to see what happens when Stiles is finally eighteen. But Stiles knows that they are just falling harder and harder for each other, each days that passes, without so much as kissing. He’s fairly certain of “what will happen” when he is actually allowed to put his lips all over Derek. And he also believes there is no way that the others hasn't picked up on all the sexual tension and Stiles stupid heartbeats whenever Derek is petting him or talking to him or being in the same room as him… God, he is so screwed. He hopes Derek’s heart is also racing, at least sometimes. But he gets it. This is their thing. So he nods.
“Okay, no prying.”
Stiles enters the Hale house nowadays without knocking. Nobody knocks really, except for everyone's parents when some of them are included in larger pack meetings or just invited for dinner. He can hear low voices from the living room but he is thinking that he'll just sneak up and get some alone time snuggle with the Alpha. Not that it'll be the sexy kind of snuggles, yet, but Derek is big on spooning and he can't deny pack. But Stiles doesn't get very far.
“Stiles!” Erica sings when he pass the entrance to the living room. She's looking up from a laptop screen, Jackson to her left and Isaac to her right on the couch. They look all very… happy. Stiles is changing his course and heads for the wolves in the den instead of the lone one upstairs.
“So what's up kids? What’s the 411? What's the hot gossip?” He tries to sound as second-y in command-y as he possibly can but realizes he's failing miserably. The others don't really seem to care. He silently hopes they don’t get the reference.
“We’re changing our relationship status online!” Erica practically beams at him and waves him toward herself. Isaac scoots over so he can press in between them. He is biting his lip smiling and Stiles smiles back. Reyes smells like roses but when Stiles takes a deep breath through his nose, he can scent them all. She points to the computer and it’s Jackson’s personal profile.
“So look at this,” she says and she sounds like an overly excited child. Stiles steals a glance towards Jackson on her other side, but he hides his face in her neck, not kissing, just cuddling. Stiles directs his attention to the profile online again. Erica is pointing with her finger at the screen and Stiles cringes a bit, one should never touch a screen that isn't a touch screen. But he ignores it for now and actually looks at what Erica is pointing towards. It says: Jackson Whittemore is in a relationship with Erica Reyes. Stiles gets a little confused because wasn't this a three sided thing? But Erica clicks her own name before he can figure out how to ask about this and a second later her profile page up. It says that: Erica Reyes is in a relationship with Isaac Lahey. He starts to grin and when Isaac’s name is clicked on he already knows what the last page is going to look like. Isaac Lahey is in a relationship with Jackson Whittemore.
“It wasn't possible to add more than one person,” Isaac explains beside him, voice low and buzzing with anticipation. And all of the sudden all three wolves are a bit rigid and stiff. Stiles has no idea why.
“Do you think this is weird?” Erica asks and her eyes are big and bright and almost scared. He realizes that yes, this is the first time they are going public with their relationship, but it also may be the first time they are telling anyone in private, too. And he feels proud over them and he feels like they respect him as second because it will undoubtedly be hard for them if he isn't supportive. He can see it in all of their eyes, even Jackson has given him a glance, looking for approval and confirmation.
“No,” he says, “I don’t.” And he can hear the breath of relief they all exhale. “But I definitely will be knocking on all of your doors from now on because there are things in this world-” They all groan, the seriousness of the situation flutters away and Jackson hits him over the head. So much for the leadership respect. But when he exits the room a couple of minutes later, Erica’s voice hits him lightly in the back of his head.
“Thank you Stiles.” He turns and Isaac says “yeah, thanks” and Jackson just nods his gratitude. Stiles is having a really warm feeling in his gut when he trips up the stairs. Being confided in by a large part of the pack makes him feel so very much part of the pack that he could just laugh.
From that day, the three of them are practically inseparable.