Your daughter's daughter is your grand daughter.
Your nephew's daughter is the granddaughter of your sibling (your brother or sister)
The grandchildren of siblings are second cousins.
Second cousins once removed.
Nieces are the daughters of your brothers and sisters. Nephews are the sons of your brothers and sisters.
They are your grand-nephews and grand-nieces or great-nephews and great-nieces.
Your niece and your daughter are first cousins. Your daughter and the daughter of your niece are first Cousins, once removed.
Your daughter's daughter is your grand daughter. Your nephew's daughter is the granddaughter of your sibling (your brother or sister) The grandchildren of siblings are second cousins.
Your brother's sons are called your nephews, and his daughters are called your nieces. Collectively, you can refer to them as your nieces and nephews. If you want to be more specific, you can say "my brother's children" as a general term.
You can refer to your sister's children as your nieces and nephews. If your sister has daughters, they are your nieces, and if she has sons, they are your nephews. Collectively, you can call them your nieces and nephews or simply refer to them as your sister's kids.
They are second cousins
Your daughter and your nephew are first cousins. His daughter is your daughter's first cousin, once removed.
They would be great nieces or great nephews.
Tiffany is her only daughter. She also looks after Whitney, but they are not related.
Absolutely not-- Joan has said countless times that she wishes she had a daughter...... that she has many "adopted" daughters. but NO daughters---- real or adopted.