Maybe it’s the way that Kurt moves so naturally around Blaine, shifting subconsciously every time Blaine moves.
Maybe it’s the protective tensing in his shoulders when Cooper, Mrs., or Mr. Anderson walks into a room, the subtle way Kurt moves in front of Blaine, just a teensy bit.
Maybe it’s the way the look Blaine gets in his eyes when Kurt walks into a room.
Maybe it’s the almost girlish way that Blaine gushes about Kurt.
Maybe it’s the way Kurt had been curled around Blaine the first time Cooper saw them asleep together.
Maybe it’s the ballsy ultimatum that Kurt had given him the first few days Cooper was back in town.

“What’re you doing here,” Kurt had said icily. “What do you mean,” Cooper had replied. “Look, all I know is that when you left you screwed Blaine over well and good, and God be damned if I let that happen again. So if you’re here to mess with him some more, leave, or find out what it’s like to be on the wrong end of one of the Hummel’s wrath,” the look Kurt’d had, was enough to cause Cooper to shrink back in his seat just a little.

Maybe it’s the way Kurt looked at Blaine as if he were the most precious of gems.
Maybe it’s the way that Kurt had of getting Blaine out of uncomfortable, and for the most part offensive conversations with Mr. Anderson.
Maybe it’s the amount of times that Kurt had taken a slushie for Blaine.
Maybe it’s the look of complete and utter worthlessness that had been all over Kurt’s face when he had failed to protect Blaine from the most dire of slushies.
Maybe it’s the smiles that only Kurt seems to elicit from Blaine.
Maybe it’s the glint in Blaine’s eyes at the dinner table which Cooper knows is put there because of an especially naughty text.
Maybe it’s the return of the old Blaine, the silly, sometimes borderline five-year-old-Blaine, that was brought about by Kurt.
Maybe it’s the everything that has to do with Kurt and Blaine’s relationship.

Either way, Cooper decides to go ahead and like Kurt.
And falls head first into shipping Klaine.