Sirius felt himself getting aroused once more but given the lack of clothes and what Remus was doing to him -- well, could you blame him?
Groaning and pressing into him, Sirius tilted his head to give him more skin to work with, cupping the back of Remus' head in his hand and trying to make sense of what he had meant. "Mm, say what, Rem?" Sirius mumbled, eyes fluttering shut in pleasure.