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 daughter and your niece are first cousins. Your daughter and your niece's son are first cousins, once removed.
Great-niece.
Second Cousin
your 2nd niece...!
Your grandfather's niece is a first cousin of one of your parents. Her son is your second cousin.
Your daughter's daughter's son is your great grandson, and you are his great grandfather or great grandmother.
Your brother's son or daughter is your nephew or niece respectively.
You are the great aunt/uncle of your sister's son's daughter, and your sister's son's daughter is your great niece.
Your sister's son and your daughter are first cousins to each other.
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 mother's son is you or your brother. Your mother's son's daughter is your daughter, or your niece. Your mother's son's daughter's mother is your wife, or your sister-in-law.
Your daughter's husband is your son-in-law.
Your nephew's daughter's son is your great-great nephew. Your nephew's daughter is your great niece.