how much older? in years from yourself? if its significant maybe he sees you as a symbolic daughter? I know at my old job my boss's daughter was away from college and he was always really really sweet to me in that non-creepy way- bought me lunch, asked me how my day was, opened doors etc. Later when we talked at a company party he told me how much I reminded him of his daughter and that it was nice to have such a "bright spirit" in his life.
I'm not saying THIS is the case, but it was mine- but he was a lovely man- and was probably a catch in his day.