Yes. If there is proof that the child is being neglected or is in some way endangered. The expense and degree of difficulty depends on the situation. For instance if DFS is involved, other relatives opposed, etc.
Yes, your grandfather's granddaughter could be your sister, making her son your nephew.
Niece is to nephew as sister is to brother.
sisterNo it would be Niece is to Nephew as Sister is to Brother. Niece and sister are both female, nephew and brother are both male.
Your sister's son, is your nephew.
If your sister had a son, then he is your nephew.
Your husband's sister is your sister-in-law. Her son is your husband's nephew, and therefore your nephew. The son's daughter is your husband's great nephew (or grand nephew) and therefore your great nephew (or grand nephew).
Your nephew's nephew is the son of one of your nephew's brothers or sisters. He is your great nephew.
your sister's child is your nephew
Your brother's (or your sister's) son is your nephew and you are his aunt if you are a female or his uncle if you are a male.
Your husband's sister's son is your nephew, just as your sister's son is your nephew.
Your sister's son is your nephew. You are his uncle if you are a man, or his aunt if you are a woman. Your sister's son is your nephew.
It is your sister's or brother's son, your adopted sister's or brother's son or your half sister's or brother's son. That would make you an aunt or uncle.