He is incredibly surprised in every single way at how things… progress as time goes by.
Not the part where Santana and Rachel start having sex.
Because really, that was only a matter of time.
Not much changes, besides that they share Santana's bed (because it's the biggest) and Kurt now has to try and not be home on some nights while still managing most of the house duties. It eventually gets to a point where he throws all of their laundry (unfolded) at them in bed while they're still naked when he gets back after being gone for nearly 24 hours and says "If you want to have more sex nights then help with more chores."
It mostly works.
And then…
Alright, the thing is, he's really gay. He is. Incredibly so. And not because of how he looks or how he speaks or what he wears. He's really damn gay because he really, really, really likes dick. And the rest of men. Like, as in, everything that makes men… men.
He loves it. A lot. Pretty much always has, even for his short stint in the one closet he'll never step back into.
And he thought that Santana was equally gay.
Sure, he knew she at least could tolerate sex with guys. But he also knew that she didn't particularly enjoy it, and certainly not on any emotional level that mattered.
Rachel was… Rachel was Rachel. For all her time chasing after terrible men Kurt wasn't nearly as surprised as he should have been when she eventually came out to him (and eventually Santana, down the line) as "not completely straight". She refused to put a label on it. Period. No matter who asked her, including him and Santana.
In her own words she "liked what [she] liked" and if they didn't like that they could "suck it".
Okay, so the last part were Santana's words, but only because Rachel hadn't been able to think of anything on the spot and Santana had thrown it in there.
So that's how everything works for awhile.
Kurt goes to Adam's a little more often, the girls bang (they eventually start actually dating, and to everyone's surprise it's Santana that makes those particular moves first), and the apartment stays in half-decent condition. Pezberry just ends up ordering out whenever Kurt isn't around. Except on the nights he's feeling particularly giving and cooks for them before he leaves.
He's still the one to keep everything in line, though.
Rachel may make all the lists, and the girl is definitely organized to a fault, but again, it's the little things that she doesn't always think about. Things like remembering to eat or sleep instead of running lines.
It isn't until Adam and him split up (because Adam is going back to England and Kurt obviously isn't - can't/won't - follow him that he starts to notice some real changes; the kind that catch him completely off-guard and he still doesn't know what to think of it all.
It starts small.
Really small.
Like, as in, Rachel Berry small. And with Rachel Berry herself.
He calls her, in tears even though he definitely doesn't want to be, and, oops, turns out he's interrupting "sexy times". But he's crying, and has no place to go besides home, and even though he's positive that Santana's going to shave his head in his sleep he goes back to the apartment at Rachel's insistence.
"Oh my goodness, Kurt… I am so, so sorry…" is the first thing he hears when he slides the door open, eyes red and puffy and completely unattractive. She's dressed, thankfully, and is pulling him into a tight, comforting hug the instant he steps inside.
He just barely catches a glimpse of Santana out of the corner of his eyes as his head buries itself into Rachel's neck, and he's pretty sure he sees a death-glare plus scowl there.
And possibly more skin than he'd like?
He's pulled to the couch, sat down, and Rachel takes up her spot at his left side, pulling him down against her and holding him as he just sobs pathetically about a guy he was only just starting to get to know but who had been saying and doing all the right things anyway. The small woman runs her fingers through his hair, and doesn't say anything useless like "It'll be okay" or "You'll move on" because they both know how much none of that helps at moments like this.
Kurt feels the couch dip, and he's too focused on feeling sick to flinch (sometimes Santana still manages to terrify him, and he's pretty sure that interrupting her sex with her girlfriend is the best way to tick her the fuck off). But he steels himself for the worst anyway, and then-
"C'mere, Lady Face. Hobbit over there looks like a damn teddy bear trying to hug a standard poodle." And then he's being moved. Back into Santana. Whose arms are just a little more firm and whose chest is definitely more… um… full. He doesn't have the energy to fight it. And some weird part of him doesn't even want to. So he just lets the two girls move him around until he's being held in Santana's arms, curled up between her legs, with Rachel sort of spread out half on him, her arms around his lower waist and head on his side, and half on the couch.
And that's how they sit for a good hour, until Kurt's tears have slowed and his breathing is under his control again.
Rachel speaks first, of course. "We're all sharing a bed tonight," she says, as if it's the most obvious thing ever.
But-
"Sounds good," replies Santana, not letting him speak, nor even sounding the least bit put off.
Um… But.. Wait a moment.
"…Santana's bed…? Because, I mean, I love you two, but…"
Santana's sultry (why is he referring to anything of Santana's as sultry?) chuckle vibrates through her chest and moves her boobs in a way that shouldn't be nearly as fascinating for him as it actually is. "Relax, Hummel. They're clean sheets. We hadn't started yet."
Oh. Okay. That must be why Santana isn't plotting any revenge.
In the end he relents. If only because being with Bruce would just be really depressing right now and it's not like he hasn't slept in the same bed with Rachel and Santana before.
Maybe he should be questioning the level of comfort he has with cuddling it up with these two women, and how nice it feels, given that he definitely isn't nearly as comfortable with any other women, but at this point he'll take anything he can get.
Besides.
It's only one night, he's sure. The three of them may be close, but Rachel and Santana are like, a thing. There's no way they'll want him around and interrupting their couple-time/sleep-time for more than a day or two. Three at the very most.
Kurt still isn't sure how he managed to be so utterly and completely wrong about something that seemed as obvious as it did.