Despite his best efforts, he can't stop a look of surprise from crossing his face. It's simply too great a coincidence, even if he doesn't dare say a word about the identity of his own father. Those who know already know; telling anyone else could be dangerous.

"Are you sure it's really okay...?" With his parents, or with anyone else who might taking issue with the child of a low-born dog associating with the legitimate son of a duke.