A grand-aunt or grand-uncle is a grandparent’s sibling, while great-aunts and great-uncles are more distantly related. However, “grand” and “great” are frequently used synonymously.
In the same way that the parents’ parents are grandparents, the parents’ aunts and uncles are also grandparents. Similarly, a person’s great-grandparents’ siblings are great-grandaunts, and when the generational gap widens, additional greats are added. Although grand-aunt or uncle is the legal title, grand-aunts and uncles are sometimes referred to as great-aunts and uncles, and many families use the term “aunt” to refer to grand- and great-grandaunts and uncles. The term great- or great-grand-aunt refers to sister-in-laws as well as sisters by blood.