You granddaughter is a great great niece of your aunt. Your aunt is your granddaughter's great great aunt.
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.
If you are a woman, you are great great aunt to your niece's granddaughter. If you are a man, you are great great uncle to your niece's granddaughter. In either case, your niece's granddaughter is your great great niece.
Your sister's daughter is your niece. Your sister's granddaughter is your great niece Your sister's granddaughter's daughter (your sister's great 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.
Your sister is the great-aunt (also written great aunt) of your granddaughter.
The mother of your uncle (by marriage) is not related to you. Neither are any of her other descendants or relations.
Your aunt is great great aunt to your son's daughter (your granddaughter). Your granddaughter is your aunt's great great niece.
Your granddaughter is your sister's great niece. Your sister is your granddaughter's great aunt.
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.
The great great grand daughter would be my cousin sister.
Your son's daughter is your granddaughter. Your sister is your granddaughter's great aunt.
great aunt
your niece