Native American Indian Dreams?

Does anyone know where i can find information about Grandfathers coming to their granddaughters in dreams? I have read this is a Native American tradition? My grandfather has been coming to me in my dreams and it is a very profound experience. I am trying to figure out if its related to him being Sioux Indian or not? I have no knowledge in this type of stuff so if i have said something wrong please keep that in mind and you have my apologies upfront. =)