A year and a half ago, Arran wouldn't have hesitated to say Roger was very much like his brother. A lot had changed. "I've known you literally my whole life," Arran said. There hadn't been a time, ever, that Arran hadn't had Oliver. "And - I know how your brain works, I think." Obviously, you could never really know, but Arran thought he probably had a better understanding of how Oliver thought than anyone else in the world. "I know that you wouldn't go through with it if you realised it would hurt me." Yes, there was a chance Oliver wouldn't realise, but the moment he did he would stop.
It wasn't the same with Roger. "I don't know whether Roger realised what he was doing." And, Arran thought he knew Roger pretty well too, and he thought there was a chance that Roger would have realised it would hurt him and done it anyway. It was a chance he couldn't completely disregard. Because Roger was, not to insult Oliver, quicker-thinking. Unless he'd been very drunk, or in some state of high emotion, he would have realised, and he'd done it anyway. "He's not you." He wasn't explaining himself well at all.
"Maybe I was always wrong," Arran said. Maybe he'd thought Roger was his brother, but Roger had never felt the same. Except, even as angry as he was, Arran didn't believe that. They'd been close, and it had been mutual. Not to mention the fact that Roger had reached out to him, accidental though it was, after his awful Father's Day. With a disgusted snort, Arran ran a had through his hair. He knew he'd given Oliver a bunch of half-finished thoughts and nothing concrete. "Telling you was supposed to be the easy one," he complained. "When did you learn to ask such difficult fucking questions?"