You granddaughter is a great great niece of your aunt. Your aunt is your granddaughter's great great aunt.
Your aunt is great great aunt to your son's daughter (your granddaughter). Your granddaughter is your aunt's great great niece.
Your sister is the great-aunt (also written great aunt) of your granddaughter.
Your great aunt is the sister of your great grandparent. Her granddaughter is your second cousin and her great granddaughter is your second cousin, once removed.
Your granddaughter is your sister's great niece. Your sister is your granddaughter's great aunt.
Your brother's granddaughter is your great niece and you are her great uncle if you are a man, or her great aunt if you are a woman..
Your her great great aunt!
great aunt
Your sister's granddaughter is your great niece and you are her great aunt (if you are a woman) or great uncle (if you are a man).
You are the great-great-aunt/uncle to your niece's granddaughter. This means that your niece's granddaughter is your great-great-niece. The term "great-great" signifies that there are two generations between you and your niece's granddaughter.
Your granddaughter's husband might be called your grandson-in-law, although the term is rarely used. Hissister is your granddaughter's sister-in-law, but is not related to you.
Your niece's granddaughter is your great great niece. You are her great great aunt (if you are a woman) or her great great uncle (if you are a man).