Disclaimer: I don't own Revolution and never will. No copyright infringement intended.
Miles Matheson hasn't cared about anything or anybody in over fifteen years. He built his wall up so high that nobody could scale it, but somehow, Charlie broke through it. He's not sure when it happened, but when his niece won't wake up, his wall has (temporarily) fallen down completely and he's thisclose to losing it. She wormed her way in and he refuses to let someone else he loves dies because he's not sure he can handle that. He knows he'd go right back to Bass if she died because Miles Matheson isn't as strong as people believe. He's human just like everybody else and he makes mistakes. (The Monroe Republic was his biggest yet.)
Miles is aware that he's probably overreacting by forcing Charlie to sit for three hours, but he doesn't care. He wants to be sure that she's okay and won't slip into unconsciousness again because last time way entirely too long for his liking. He can't explain the feeling that rises up within him when Charlie tells him she came back to him because no one has cared that much about him in years. He plays it off since he'll end up near tears again if he acknowledges that he's glad she returned because of him, and that's not about to happen again for a long time. He can't let it because he has to save Danny. Ben trusted him to do this job, and he's going to do it to the best of his abilities.
He will not let Charlie down because he loves her and she's currently the most important person in his life. They're dependent on each other now.
Charlie isn't surprised that what brought her back from her "perfect" life with her father, Maggie, and Danny is her uncle. Besides Danny, her only family now is Miles. She's not sure she can be without him now, especially as he's saved her so many times.
The realization that she cares about him, that she loves her uncle is a little surprising. She has walls up too, scars from her mother dying, and those won't ever go away. But leaning on Miles, even with all his secrets, helps. She'll let him keep his secrets and obvious issues to himself, but Charlie is determined to break through the walls he's put up.
Nora and Aaron are important to her, and they're family now, but Miles means so much more to her. He doesn't want to be there – That much is obvious – but he is and that is all that matters to Charlie. She just hopes that when Danny is saved (and hopefully, the Monroe Republic is taken down), he'll stay true to his word and won't leave her. Everyone has left her, and she can't handle anyone else abandoning her. It'd be one hurt too many and she thinks she may snap since she's on the verge of it all the time.
Charlie and Miles are keeping each other sane and their love for one another keeps them upright most days when they feel like falling apart. There will be secrets ( betrayals) revealed, but in the end, the uncle and niece's bond will only be stronger after coming through the other side. They're family and better together.