Erik's look of surprise is so complete in another moment it might be comical, eyes widening to a degree that's actually perceptible. None of this, as Charles will be aware, is affected, of all the things he might have expected to come out of Charles' mouth, none of them were ...that. Mostly because he just hasn't thought about it; there's been nothing to think about amidst all the other clamoring confusion and his own wrenched sense of unfairness.
But he wouldn't have done as much anyway. He doesn't mull; the topics his mind engages are concrete, sequences of images that will shape the future. No abstracts like hope or ambition, only plans. So he has not thought about what this means inasmuch as it seems ...obvious, laid out like a topographical map, and as tangible. To name the thing that he and Charles have become makes it part of a world where he's never taken the trouble to consider staying, only visited with the ease of a person who knows he's a visitor. He is not bound to that currency of culture, and wouldn't voluntarily become so if asked directly. It strikes him as pointless to quantify, who he takes to his bed, and it's never figured into his outline of the separation of the self from the other.
All of which is just so much mulling, these are facts: he'd chosen a different room to Charles' without lingering on whether or not such a state actually was a choice, and hadn't thought further until he was trying to fall asleep. Then he'd wanted Charles there, and it had crossed his mind as sleep pulled him under to at least be annoyed by the rigamarole that would involve.
"I haven't thought about it," he admits, in light of this, an thing which is rare from Erik just for being what it is. "Stop looking so sorry, this is hardly the worst thing to happen to me today."
That that should be a joke may be entirely lost on Charles at the moment, but that's what it is, a biting little thing that only closes teeth on itself. "Of course I want to do this. This," he demonstrates, picking up both of Charles' hands in his, "is not about getting you into bed, I'd hope that's obvious."
That 'this' will stay nameless as well as secret doesn't occur to him to verbalize.