Not if they have guardianship.
i think its a GRAND niece instead of great niece and u would be a grand uncle or a grand auntie to her
Your sister's aunt (who is also your aunt) is the baby's great aunt. The baby is a great niece or great nephew of your sister's aunt.
Your sister's daughter is your niece. If you are a woman, you are your niece's aunt; if you are a man, you are your niece's uncle. Your sister's son is your nephew.
Yes, he is her uncle
For clarity, lets call your great great grandfather's niece "the niece". The relationship sequence: (1) The niece is the daughter of your great great grandfather's sibling (2) The niece is a 1st cousin of one of your great grandparents (3) The niece is a 1st cousin once removed of one of your grandparents (4) The niece is a 1st cousin twice removed of one of your parents (5) The niece is your 1st cousin three times removed
A niece or nephew is the child of an aunt's or uncle's brother or sister. So the parents of the aunt/uncle and of the niece's/nephew's parents are the same people - their grandparents. The grandmother of the aunt or uncle is the great grandparent of the niece or nephew.
For clarity, lets call your great great grandfather's niece "the niece". The relationship sequence: (1) The niece is the daughter of your great great grandfather's sibling (2) The niece is a 1st cousin of one of your great grandparents (3) The niece is a 1st cousin once removed of one of your grandparents (4) The niece is a 1st cousin twice removed of one of your parents (5) The niece is your 1st cousin three times removed
There are several possibilities, including "no relation" (or at least none that can be described more concisely than "great uncle's niece"). Assuming the maximum possible degree of consanguinity, your great uncle's niece could be your mother. She could also be an aunt (your mother's or father's sister, depending on which side the great uncle is on), or as mentioned she could be "no relation" (if the great uncle is an uncle by marriage and his niece is the daughter of one of his brothers or sisters).
Your niece is the daughter of your brother or sister. She can have any name her parents choose for her.
Your great great grandmother's niece is the daughter of her brother or sibling and thus the first cousin of one of your great grandparents. Therefore, the niece is your first cousin, three times removed
Your aunt is great great aunt to your son's daughter (your granddaughter). Your granddaughter is your aunt's great great niece.
Nothing. You may choose to call him "my niece's husband", "my nephew in law" (but that's pushing it) or by his name.