Your daughter's grandfather's brother's son is her mother's or father's first cousin and her first cousin, once removed.
your second nephew
cousin
3rd cousin
Your grandfather's niece is a first cousin of one of your parents. Her son is your second cousin.
What is your great-great-great grand nephew?!
Your son would be the uncle of his brother's son.
Your sister's son is your nephew His sons are your grandnephews, and his daughters are your grandnieces.
Second cousins once removed.
Your grandmother is first cousins with cousin. Your parent would be the second cousin of the cousin's son. That would make you second cousins once removed.
Your grandson is the great-nephew of your brother.
Your sister's son is your nephew His sons are your grandnephews, and his daughters are your grandnieces.
Great niece