"I don't care if it's obsolete." Kevin maintained as he exited the car, "Two-hundred-billion songs on your phone is awesome, but a thousand years from now vinyl will still be cool."
See?! This is the geek bond Kevin can only have with Castle. I think they were both really happy to meet each other.

During the whole Heroes show, as soon as we learned about the triplets, I expected Barbara to show up.
But she didn't. :/

This is it, isn't it? This is what Kevin in the future meant about Javier hurting him. It's just his awkwardness and solo freaking out over everything, thus shutting his best friend out in the process.
I mean... I don't know yet for sure, but I think, aware or not, Kevin's been waiting for Javier all along.
What has me thinking this is the famous picture 2010!Javier has from 2018!Javi in his own life. The way he was shocked at the way hsi hand was so naturally resting intimately on Kevin's hip.
Didn't he note that Kevin was beaming in the picture?
So maybe that was the last time Kevin's been happy around his partner. For since then, Javier's been off, big time.

Huh. So the trouble started before, then.

AAAAAAAAAAARGHHHNNNNN... Of course I'm not gonna go to bed NOW.