They couldn't fight it any longer. And they had fought it, with that innate Eppes' stubbornness that seemed to be a genetic trait. For years they had let that fight control everything, afraid of what would happen if they ever gave in.
Charlie had run all the way to England fighting it, unable to continue dealing with his brother on a day to day basis. Never knowing what the next day would bring, acceptance or rejection, love or hate. He couldn't bare it anymore, needed desperately to be somewhere else, somewhere far away from the temptation, where he could focus his energy on more positive things. He was tired of pretending every day that he didn't notice it, didn't notice Don moving further and further away. It was easier to keep that mask in place with more distance between them, easier to tell himself that it didn't hurt so much.
Don had cut off all connection to his family fighting it, unable to handle talking and seeing them without saying and doing what he really wanted to. It had hurt more than he thought possible, but to him that attempt at a clean break had been better than the slow painful tearing of the bonds between him and Charlie. Though now he would hesitate before deciding it was the better decision, after knowing just how much he had hurt his family through his actions. He knew that he had worried his parents unnecessarily, but it was brother that he had hurt the worst. Charlie was still so uncertain around him, never sure that Don wouldn't cut him out of his life like that again.
Things had gotten better, slowly but surely. Working together had definitely helped, allowed them to spend time together and bond, without getting too distracted by other thoughts. Still the continuing fight wore on them. They had both hoped that with the passage of time, these feelings would have diminished; instead they had grown even stronger.
They craved for each other desperately. Thirsting for the other's presence like they had been in a drought, deprived of it through emotional and physical distance. Even without giving in, they were hopelessly addicted. Hungering for some nameless thing that they knew only the other could ever give them. They found themselves making up excuses to be together. Don calling Charlie in for cases where he wasn't really needed. Charlie doing work for Don even when his other consulting jobs demanded his attention and his projects suffered.
They had fought it for years, sometimes it seemed forever, but no longer, enough was enough. They had finally given in, the yearning for the other too much to fight anymore. Soon being together wasn't enough, they needed more. Neither was truly surprised when it became a common occurrence for them to cuddle on the couch together in front of the TV. Then even that wasn't enough, finally conceding to sleeping in the same bed, after a week of restless nights, their souls crying out for each other. And finally the last of their boundaries slipped away, as skin touched skin, answering a demand that had been mounting for decades.