Your niece's son's daughter is your great grand niece. Your niece's son is your grand nephew or your great nephew, whichever term you prefer.
Great-niece.
your 2nd niece...!
A second cousin.
Grand niece.
Nieces are the daughters of your brothers and sisters. Nephews are the sons of your brothers and sisters.
You are her great-great Aunt (or great grand Aunt, depending upon your preferred nomenclature). She is your great great niece.
Second Cousin
Nephews and nieces
my cousons sisters boyfriens dads nieces grandma's favorite sons dogwalkers mothers friends mum twice removed uncles daughter
Your daughter and your niece are first cousins. Your daughter than your niece's son are first cousin's once removed. Your daughter's child and your niece's child are second cousins to each other.
Your niece's son's son is her grandson. He is your great great nephew and you are his great great aunt or great great uncle, depending on your gender.
Your borther-in-law's children are your nieces and nephews. You are their uncle or aunt, as is your spouse.