How long has Keefe liked Sophie?

He doesn't start showing visible signs of having feelings toward Sophie until Exile but in book six, it talks about Keefe getting so upset after Sophie's funeral, that he was willing to sedate himself over and over again, night after night to cope with the loss. He was quite clearly distraught but was that just from losing a friend, who he wasn't even that close to at the time, or from losing his love? And if there are any of you who may argue that Keefe doesn't love Sophie, I would advise you to read Neverseen again or The Talk by Shannon Messenger- the short story at the end of Flashback. It may be the most adorable thing I have ever read.