Nephew-in-law! However, most people leave off the in law but in technical terms, it is nephew-in-law.
In-laws are not related.
Yes
they would be brother in laws
Nothing. Your niece in law. Your brother in laws niece.
If your brother adopted you, you are his son or daughter and his in-laws are your grandparents by adoption.
Since it would be your sister who had the child with her husband (your brother-in-law) then that would make their child your niece or nephew.
They are brother-in-laws.
You would be her aunt. She would be your niece.
There would be no relationship as you do not share a common ancestor. If your brother-in-law is married to your sister, then her daughter is your niece, her husband would be referred to as your niece's husband.
Your sister in law is your husband's sister or your brother's wife.
Your brothers' in-laws are an attachment to your family by marriage, so they would be classified as in-laws by yousome people call them familys in lawsome call the second cousins
It depends on the trial and the laws in your jurisdiction.