Being honest isn't "clueless". I know it seems like an unsympathetic, ruthless thing, but it's not at all. You would caringly explain what's going on, tell them it's okay to be sad and encourage them to ask questions. I have ~25 students each year, and they deal with pet deaths, family deaths, family incarcerations, family drug use, deadbeat parents, homelessness, etc.
The truth + caring/listening/support = the best you can do.