The order in which Alan says those names may have been a bit of a mistake because the moment he says Jack's name, Edwin's expression closes off entirely.

"Jack Alston. I see."

What precisely he sees, Edwin is not elaborating on. (He is, of course, not completely uncurious about the fact that Alan has also named Robin's sister but the fact that this man is apparently a friend of Hawthorn's makes Edwin immediately suspicious enough to eclipse that for the moment.)