Dreams like this used to make Erik feel guilty.
That was before Charles had gotten a whiff of one of them, not long after Erik had moved back in. "I'm not upset," he'd said, giving Erik a sly look. "Do you think I never fantasize about the way your ass used to look in a wetsuit? You don't need to look so gutted that I caught you dreaming about mine."
(Why Charles had then been so surprised when Erik immediately went out to the nearest sporting goods store to prove exactly how well he could wear a wetsuit at fifty-five, Erik didn't know— but there'd been no more noise out of him about whether or not Erik could still pull it off.)
So: Charles had as good as given Erik permission to enjoy these dreams when they came. Erik wasn't about to squander this one. Even once he'd woken up enough to realize he was dreaming, he kept it going, until 1962 fantasy Charles was on top of him, driving into him, Erik's heels pressed into Charles' (also magnificent) thighs and his hands clutching that beautiful, round—
"Is there some reason we're always here for this?" Charles asked, sounding remarkably unaffected for a man who was supposed to be fucking Erik into the mattress.
By 'here,' he meant Magneto's lair circa 1978, which had been decorated in as aggressively seventies a fashion as Erik could manage. The seventies had been the best decade, the one most closely attuned to Erik's own natural sense of style. He still resented having missed out on the first few years, and had made up for it by skipping the eighties. His one regret about leaving it had been that he and Charles had never had sex on that couch.
"You won't let me paint the bedroom," Erik said. He was distracted now, losing the thread of fantasy, dream Charles having gone still, already half-forgotten.
Charles laughed. "Ah, yes. My ongoing vendetta against anything in purple and red. Well, I'm going to keep being unreasonable about that one, I'm afraid."
Erik woke up shortly afterward. He was hard, with one hand massaging himself through his pajama bottoms, and the other petting his Charles' ass. Erik had been the big spoon when they went to sleep, but Charles had turned himself over halfway through the night, so that he was now facing Erik. He had snuggled up close, so that Erik could feel his breath every time he breathed out.
"Are you awake?" Erik asked, pitching his voice low enough that if Charles weren't, Erik hissing at him would be unlikely to rouse him. It was July, and summer vacation was, along with winter break, the only time Charles ever, ever got anything even approaching enough sleep. He had been running himself ragged for twenty-five years, and would for twenty-five years more, for the rest of his life. Even Erik's return hadn't slowed him down, and for every task Charles decided to delegate to Erik or anyone else, it seemed he took on four more for himself.
Charles responded with a low, sleepy murmur, and so Erik lay there for another hour, eventually falling into one of those half-asleep fugue states. He spent it thinking about Charles' ass— not Charles' ass circa 1962, but Charles' ass circa now. It wasn't what it used to be, but neither was anything else about him, really. About either of them.
The next time Erik woke, the sun was up, and so was Charles, who had snuggled even closer in the meantime. He was nuzzling Erik's neck in-between yawns and playing with the waistband of Erik's pajama bottoms. Erik was getting hard again. His hand was still on Charles' ass, and he didn't move it until some time after that.