Hospice workers noticed that dying patients frequently dream of family or friends who have died before in this article
I have noticed for years that people can have spiritual or vision dreams where it feels like the deceased friend, relative, or lover is actually there. That is, the dreamer believes they can see, hear, touch, and smell the person they knew so very well. It feels more like a visit than a dream sometimes.
See the many different types of dreams in my book at http://www.drstevenfox.com