Your husband's niece is your niece, too. You and your husband are her aunt and uncle.
Your brother is not related to a niece of yours who is the daughter of your husband's sibling.
Your niece's brother is your nephew.
that would be your niece or if you want to be fussy then your niece in law!
Your mother's brother is your uncle. You are his niece (if you are femlae) or his nephew (if you are male).
Nothing. Your niece in law. Your brother in laws niece.
Your half-brother's daughter is your niece. Your niece and your son are first cousins to each other.
Your brother's daughter is your niece. Her daughter is your great niece.
your brother's daughter is you niece
niece/nephew
Great niece
who knows who cares
niece
Technnically, she is not related as you do not share a common ancestor. She would refer to you as Aunt and she is your niece. Whether he is your first, second or fifth husband, his niece is your niece while you are married to him.