Your nephew's son is your grand nephew or great nephew. Some people say one, some say the other.
Your sister's son, is your nephew.
A brother's son is referred to as a nephew.
The son of either your sister or your brother is your nephew. The English language does not make a distinction in that.
Your nephew's son is your great nephew and you are his great aunt or great uncle.
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 sister's son, is your nephew.
In English language terms for family relationships, there is no relationship called "nephew once removed." The son of your nephew is your great 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).
nephew
Nephew
A siblings son is always called a nephew
Your nephew