This story demands careful rereading: It's an elegantly tangled and perfectly dysfunctional incestuous knot of mutual manipulation, loneliness, and desperate yearning. "Oblivious narrator" as Severus is, in all his insular awkwardness and resentment, he manages to come away from this most inappropriate of "family" summer vacations feeling that, if he was used, he gave as good as he got.
More digging and contemplation is required. A wonderfully complex story with an achingly believable young Severus at its heart.