Sam is curious about the weird thing Blaine seems to have about Kurt’s neck. So he investigates.
He doesn’t really notice it right away because he’s getting used to city life - it’s kind of fast, but it’s exciting too, and modeling just might be his thing - but it doesn’t take that long for Sam to grow suspicious about his best friend and his best friend’s fiancé.
Maybe it’s just because he’s shorter, but whenever Blaine hugs Kurt, he tends to turn his face into Kurt’s neck, sometimes kissing him there before he lets go. And Sam, well, he’s not gay or anything, but he’s starting to find himself wondering what’s up with Kurt’s neck that makes Blaine do that all the time.
"Dude, can I ask you something?" Sam says during one of their video game parties with Artie. Blaine’s focused on the screen so he doesn’t respond right away, and when he does, he’s obviously distracted.
But Sam in ‘Hold Onto 16’ he says “I miss being a teenager” and the next year he and Blaine act like total dummies and dress like super heroes and Blaine helps him forget about his troubles and wow are those tears
"Are you about to throw a coin in the East River?"