Gaius leaned into the caress of Sirius' hand, and his eyes crinkled in amusement at Sirius' introduction. He was just a wee bit old perhaps to be a "boy" friend, but it didn't matter a bit, so long as Sirius was willing to claim him in one way or another. Especially in front of an old friend, corporeal or not.
"No, I don't mind," he replied, stepping back slightly so that he could regard James with just as frank an appraisal as the ghost had given him. He arched a brow. "Hullo, James. Sirius and Harry both have told me so much about you. I must say, from their descriptions I was expecting someone ten feet tall who plucks dragons out of the air and eats them raw. Makes me wonder now if Sirius has exaggerated other things."