Your niece and nephew.
The daughter of your husband's brother is your niece.
Your daughter's son is your grandson and you are his grandparent.
Your daughter and your sister's son are first cousins to each other. Your sister's son's daughter (her granddaughter) and your daughter are first cousins, once removed.
A son's wife is called your daughter-in-law.
A daughter
You would call your daughter's son by his name ex: Hi Jack.
His name.
Your daughter is your sister's niece. Your daughter's son is her great nephew.
daughter...daughter in law.
Your grandson.
daughter in law
daughter in law
Your grandson.
Your son-in-law is your daughter's husband.
Your grandson.
you can call him your nephew if you are mom's daughter's sibling or if you will be the mom you can call him your grandson.
Your father's brother's son is your first cousin and your daughter's second cousin.