A great-grandparent is read as the deep roots of the family, reaching back past living memory. Dream tradition sees the figure as inherited strength and stories waiting to be known.
Has this come up in your dreams before? What was going on in your life then?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.