You would be a first cousin by marriage, in other words, there is no direct relationship between you.
Anna Eleanor Roosevelt and her husband, Franklin D. Roosevelt, had a distant family relation as fifth cousins.
Second Cousin
Great-niece.
Nephews and nieces
your 2nd niece...!
They are your nieces and nephews.
Your borther-in-law's children are your nieces and nephews. You are their uncle or aunt, as is your spouse.
He is their Uncle and they are nieces and nephews.
They would be great nieces or great nephews.
They are your great nephews and/or great nieces. Alternately, some people say grand-nephews, grand-nieces.
It says what relation are your brothers nieces to you.... It could be your child or your niece also causes you can have two brothers and it may be the other ones kids. Or of course it could be your brother's new wife kid by another man making her no relation.
The children of your husband's siblings are your nieces or nephews. Their children are your great-nieces or great-nephews.