Members of the Family

There is no such thing as a great-uncle. Your grandparent's brother granduncle. Your great grandparent's brother would be your great-granduncle. Basically, within the generation, leave the greats and grands alone, and just change "parent", "father" or "mother" to "uncle" or "aunt" to denote that ancestor's sibling. For example, your great-great-great-great-grandfather's sister would have been you great-great-great-great-grandaunt. You won't usually call someone that in the same way you would a father, but it is a very important distinction to make when discussing genealogy, as you wouldn't know what error was made if someone talks about his "great-great-uncle".