His Aunt
brother
Your brother or brother in law
Your niece's brother is your nephew.
Cousin brother
niece/nephew
nephew
Your brother's son is your nephew. Therefore, your brother's son’s son would be your great-nephew. In summary, your brother's son son is your great-nephew.
Your brother-in-law's son is your nephew
If your niece's is by your sister but the brother is by your sisters new husband & another woman there would be no blood relation. If not then he's the nephew
Your brother's son or daughter is your nephew or niece respectively.
Your fathers brothers are your uncles. You are their nephew, or niece.
Your mother's brother is your uncle. You are his niece (if you are femlae) or his nephew (if you are male).