I remember having a dream about my dearest sister, with whom I was (and am) very close, when I was 20, and had moved away. I dreamt she died, and I had to wash her body for the funeral. I cried and cried and cried. We had shared a room all our lives, and then we were separated, and it was really, really hard. I think I dreamt that dream because I was grieving the loss of our closeness, that what we'd had was gone and was not going to come back.
I had many very realistic and graphic dreams of my sister dying when she moved away for college (we had also always shared a room).