Harry was thankful when Severus took the question. Faustus was his son afterall, and he had been trying to avoid incriminating Severus. The kid was intelligent though, definitely a plus in these times. The last thing Severus or him needed was Faustus blabbing about Harry being in Severus's rooms.
"Not everyone knows that your father and I are friends also." Harry added, "You may at times see us act differently around other people. Usually we act barely civil. It gives an element of surprise with some people." Harry gave a small snicker, "And we find it amusing I think."