"Then it's a deal." While Harry tends to be a private person, that's only because so many people seem confident that they know the 'real' him. Black doesn't seem interested in presuming all that much. With the truth and news as payment, he wonders how best to put the deal between them. Why not treat the arrangement like veritaserum? "And you're welcome to ask about anything or everything, but I do reserve the right to say no. I won't lie, but I might not be willing to answer."

"Oh, I'm sure, but given that I'm the last of it, at least in my, er, timeline?" Is that the word? It sounds a bit sci-fi. "I think I'm allowed to call us kin."