Cas was paying zero attention to his surroundings. Later he might feel bad about this, but right now he couldn't really hear the two of them talking anyway. He only knew he really enjoyed Dean's hand in his hair, intentionally bumped his head into it in an offer for it to become a firmer grip and slide off of that cock again in order to breathe -- even then he offered little licks and kisses in replacement.
He was, of course, a little sad at the loss of Samandriel's touch -- but since no one had told him he couldn't touch, Castiel gave up some of his already wobbly balance in order to do it himself. "Please," he said, tone wrecked gravel. He had no idea if he was saying it to Samandriel, or Dean. At this point, probably even Lucifer would have been good enough.
Somehow, it was Lucifer’s tenderness with him that shoved down the walls in his brain that were allowing him to ignore how good everything felt. Castiel’s absolutely broken voice joined with those words and eyes squeezed shut, Dean came, silently, teeth clenched and jaw twitching in a struggle to keep every sound locked up inside of him. If he let them out, Lucifer might well have gotten the tears he didn’t want and frankly Dean was real tired of having his emotional armor pushed to that point. His fingers squeezed tightly into Castiel’s hair as though that might keep him grounded as well.
“Go on,” Samandriel allowed, torn in so many directions with how attune he was to the varying emotions in the room. Castiel didn’t need Samandriel’s cock to get off, but he managed to time things exactly to where his brother came to that point of no return and the younger angel pulled out before he too ended up there.
"You're okay," Lucifer said, kindly -- and this time it was directed toward both Dean and Castiel. "Beauitful." He kissed Dean one more time before leaning back, giving space where he felt it was necessary. Dean hadn't gotten permission, but Lucifer wasn't the type to actually be angry over something like that. Instead, he gestured for Samandriel to come nearer to him.