Dictionary.com explains that a great niece is identified as the daughter of one's niece or nephew. One's niece is defined as the daughter of one's brother or sister. One's nephew is defined as the son of one's brother or sister.
Similarly, a great nephew would be identified as the son of one's niece or nephew. A great niece or nephew could also be affectionately referred to as a grand niece or grand nephew.
In reverse, one's great niece refer to their grandparents' sibling as either a great aunt or great uncle. These terms can also be used interchangeably with the terms grand aunt or grand uncle. It is important to distinguish the proper terms for one's relatives when researching family history or creating a family tree. Parenting.com states that creating a family tree with a loved one or family member can be a great way to learn about one's family history and bloodline.
According to Parenting.com, building a family tree can be very important when it comes to maintaining one's health. Certain diseases and health disorders are genetic, and they can be known to run in families. Knowing about one's increased risk for diseases, such as heart disease or anemia, can be extremely beneficial in preventing many serious health conditions.