If your family is agnostic about death, then you could invite your child to imagine what happens. When my four-year-old cousin asked me, “Where do people come from?” I started to explain that babies grow inside someone’s belly. She interrupted me, “No, like where did the first person come from?” I decided to ask her what she thought, and she replied, “I’m thinking they came from the ocean,” and she went back to playing. Sometimes you don’t have to know the answer.