Once, Finn Hudson would feel awkward walking in on Kurt and any boy even sitting close. He even worried, offhandedly, if he would ever walk in on Kurt and Blaine (once they were official) doing anything because it wouldn't be like Kurt hasn't walked in on him and Rachel (the summer when they were sharing a bedroom) or him and Quinn (more recently) before. Granted, it wasn't anything totally scandalous that Kurt walked in on - maybe the beginnings of a make-out session- but it was enough for Kurt to blush and duck away, hands covering his eyes.
So it's rational for Finn to worry, just a little, that he might walk in on Blaine and Kurt one day - because Blaine and Kurt were boyfriends and Finn would be even MORE worried if they DIDN'T kiss or makeout, honestly. It's not the gay thing, either - Finn knows he's come a long way; knows he's grown up a lot. It's more a brother thing, or a friend thing. He doesn't look at Kurt like someone to make out WITH, and before Blaine Kurt hadn't had any boyfriends so he's just getting used to the idea, really.
But if Finn's learned anything the past couple of months since Kurt and Blaine started dating it's that they're intensely private. He hasn't even seen them hug, not really, not until Blaine sings to Kurt in the courtyard. He didn't see them really touch one another again until prom, but even then it was for pictures before the dance, and even THEN it was just slightly clasped hands and leaning into one another's space. He knew they danced together later, after Kurt won Prom Queen, but he wasn't there for that. No, by then he was sitting on the curb outside the school next to Jesse St. Douche waiting for his Mom to come get him. How embarrassing.
And you might say that it's not so weird not to see Kurt and Blaine together, being physical in any way, but Finn's around Kurt A LOT these days. He and Kurt are closer than he'd ever thought he'd be. They watched movies together, they chat in the kitchen doing dishes, they bond over music (the Beatles transcends genre) - and because Blaine is basically Kurt's best friend (and boyfriend, these days) he's often there, too. He's joined their conversations, their Friday night dinners and he's jammed with Finn so many times now that it's hardly weird (he'll even text Blaine on his own, now, and invite him over without even asking Kurt. He was worried Kurt would feel put out, but he ended up being pleased to see them playing guitar in the living room when he came back from getting brunch with Rachel.). Finn considers Blaine a friend, and he likes the other boy.
He doesn't want Kurt to not feel comfortable touching his boyfriend in front of him, though, not at all. The thing is that they sit far away on the couch; they don't hug hello or goodbye, and sometimes it's painfully awkward to see the look in Blaine's eye when Kurt says something witty and so Kurt-like. They get all soft-like, and adoring, and Finn can tell he wants to kiss Kurt then - because that's the look Tina gave Mike, or Puck gave Lauren or, at one time, Rachel gave him (and he supposes he gave Rachel? Or Quinn? But he can't see his own face, so).
So he vows to talk to them about this because, no, he doesn't want to see them make out, but if Kurt wants to kiss Blaine hello or goodbye or cuddle with him on the couch when they watch a movie or hold hands - that's fine! He should. Finn wants him to and he doesn't want their relationship to be strained because of him.
He talks to his friends first, though, on how to approach it, and in the end, they're no help (he should've known this). They're a plethora of random ideas and thoughts that end up nothing to do with the problem at hand ("They're two dudes, right?" Puck says, with his matter-of-fact face, "I have no clue how they keep their hands off each other, dude. Like, as dudes wouldn't sex be on the brain all the time?").
In the end, he bounds through the front door of the house later the afternoon (he'd stayed with Rachel after Glee to go over solos) with all these thoughts in his head about what he'd say to Kurt. He bounds in so eager that he's loud, as usual, dropping his bag and toeing off his sneakers and slamming and locking the door behind him, and he doesn't even notice Kurt and Blaine there, on the couch, until he walks right by them.
But when he finally notices, he stops in his tracks, because Kurt and Blaine are laying still and quiet on the couch, Kurt lying in between Blaine's legs with his head on his chest. They're both asleep, Blaine's fingers tangled gently in Kurt's hair, Kurt's hand tangled with Blaine's free hand, and Finn's never seen Kurt so still and at peace. He's seen Kurt quiet and withdrawn, yes - because Kurt is the master of closing off his expression and dismissing you with a slight glare - but he's never seen Kurt this vulnerable, this comfortable. They both look comfortable. He can't help but smile because he knows Kurt's wanted this for so long. So, so long.
Finn's never seen them this close, no, but he hopes it's not the first time he will. He'll still talk to Kurt about it, and things will change a bit - Kurt will kiss Blaine when he comes and goes, and Finn won't ever bat an eye - but it'll be this moment that Finn will look back and realize everything's different. That he'll realize that these two guys -one who is now his brother and the other a good friend - will probably be in his life for a very long time, if not forever. Hopefully, forever.
So he'll watch for a few more moments, and then he'll feel like a creeper and start for the kitchen to make himself a snack, but it won't be before accidentally hitting the side-table with his hip and making the lamp there tip to the floor with a loud LOUD smash.
It'll ruin the moment because they'll be startled awake and Finn will still be there with a sheepish expression when they finally look up - but Finn's Finn and that's how he does things, unfortunately.