You're 22 and the college experience is finally over, and you're all set for Quantico, for a career you think you can make your own.
University has been good; you've worked hard, had fun, made some great friends, put yourself out there and not been found lacking.
You don't see your family much, sure you head back west for the holidays, but the phone calls have become pretty irregular and while you always remember to ask how Charlie is you usually don't wait for an answer.

You're 25 and you're an FBI agent, and it feels damn good to say that. You love your job, and love the fact that you're good at your job as well. The years spent plowing through that criminal sciences degree paid off, you breezed through half your classes at Quantico and the position you have in the Albuquerque office is working well.
You're closer to home, living in New Mexico, which makes traveling back for the winter holiday less strenuous, but you've noticed that, as Charlie would put it, the distance from you to home indirectly correlates to the time between your family phone calls.
You don't know much about what Charlie is up to. You get updates on life from your mom and dad, but somehow the descriptions of Charlie's activities never have much depth. You know he has his PhD, he got that when you were 24, you know he's still at CalSci, doing post doctorate work, maybe something about teaching. The idea of little Charlie up front in a classroom, curls bobbing as he scrawls chalk across a board, well it would suit him, you guess, except all you can think of are the rows of college kids he'd be teaching, all older than him, and really, how's that gonna work?
But other than that you know nothing, and you're okay with that. You're two different people, living your own separate lives and what good is it going to do anyone for you to know every intricate detail of Charlie's life? It's all just numbers anyway.

You're 32 and your mom's dying. 32 and you're not sure if your little brother is going to make it through this.
He's 24 in body, at least mid 40's in mind, and probably 12 in heart and soul, and sometimes you think he's never going to grow up. Sometimes you don't want him to, but mostly, mostly you wish he's wake up and see the world for how it is, see it without looking through the veil of numbers behind which he lives.
He's retreated to the garage now, retreated to his math. Buried his head in numbers and unsolvable equations and minesweeper for God's sake, and your mom is dying but that doesn't seem to register.
You've never claimed to understand what goes on in his head, how his mind works, but you've never truly worried for his sanity before. But this, to you this looks like a crisis point, a lot like the end of the line and you just know you can't lose your brother as well as your mom.
But Charlie hasn't eaten the food you brought down for him and he ha s that manic, not quite stable look in his eyes, mumbling equations under his breath and you just want to shake him. Shake him until he focuses on the real world, until he focuses on you and whisper-speaks your name in that soft way he always did as a kid, because you've been here three weeks and you're not sure if he's even noticed your presence yet.