He's fifteen, still, and the students at Xavier's school are afraid of him (Good, his mind and the nightmare sand whisper to him, they should be!), afraid of his power... and of Jack's, but nobody believes, so nobody sees, and they think the ice he 'controls' is actually coming from him. Sometimes, Logan seems to almost see Jack, to almost smell him, but then it's gone, and with a shake of his head and a grunt, he shrugs the idea off and figures he must be going crazy in his old age.
Of course, Logan's daughter (clone, technically) is probably the closest to seeing Jack- after all, she was supposed to be impossible as well, so she's fairly open to the idea of spirits, and her nose doesn't lie, she definitely smells someone on Jamie, and smells his lust and embarrassment, as if something is... feeling him up.
Surprisingly, though, there is one person who can see Jack- the Professor's goddaughter, Wanda- but she's fairly magical herself, and is 'crazy', so nobody would believe her about the winter spirit anyways. Still, the three are able to get along well enough, and if the Professor and Logan notice that Wanda comes to Jamie when she needs comfort, well, they don't comment.
Her father, and the Professor's nemesis, Magneto, can see Jack too, but he's just happy to know his daughter has two friends- and if he hints that should the X-Men become to untrusting for Jamie to handle, his door will be open for the two of them, Jamie just silently nods and keeps the secure phone number well hidden.
And life goes on. Jamie is able to successfully 'walk' through the shadows now, up to three thousand miles, but the process is too cold for anyone else to come along (the Professor and Dr. McCoy give him a digital thermometer once- it freezes solid, and it's supposed to be able to handle exposure to the constant freezing whether of the arctic.), save for Jack, who finds it... creepy, but enjoyable, because it's almost like he can feel Jamie in the shadows, all around him, and it's almost like they become one mind in two bodies for a brief time while in the shadows.
North, of course, is concerned about Jamie having the exact same powers as Pitch, and Bunny is close to downright hostile (probably would be hostile flat out if it weren't for Sophie. Jamie doesn't get what his problem is, but doesn't let it bother him, because Jack gets angry enough for the both of them.), while Tooth is silently worried for him, and hopes the power doesn't overwhelm him... But Sandy and Manny are... silent, if approvingly so.