When NSYNC starts, he's glad that Justin's part of it. He has good memories of the Mouse Club and he's glad for them. What happened after it was over isn't something he wants to dwell on, and Justin's smile makes him feel sunny inside.
JC likes feeling like that, likes the shiny new beginnings unfolding. He can't help but be pleased that his kid brother from before will be there with him. He likes Joey and Chris a lot, Lance seems cool, but Justin knows him.
He sings 'High Hopes' in the shower and imagines four voices blending with his.