Most likely they would not be related to you
They are your "third" cousins.
She is your niece.
She is your niece.
Your grandfather's niece is a first cousin of one of your parents. Her son is your second cousin.
Your grandfather's sister is your great aunt.
Your brother's daughter is your niece. Her daughter would be your great-niece. You would be either her great uncle or great aunt.
Your sister would be her great aunt and she would be your sisters great niece.
Your niece in-law, or your niece by marriage.
If you have two nieces who are not sisters but are each the daughters of your siblings, the two nieces are first cousins. If they each have a daughter, those daughters are second cousins to each other.
If your niece's is by your sister but the brother is by your sisters new husband & another woman there would be no blood relation. If not then he's the nephew
They are second cousins
Some nieces of sisters are related to each other and some are not. Your niece is the daughter of your brother or sister (your siblings). If you have more than two siblings and at least two of them have daughters, those daughters are your nieces and they are first cousins to each other. You can also have a niece who is the daughter of a sibling of your spouse. If two sisters have nieces who are daughters of their spouse's siblings, those nieces are not related to each other (unless the spouses are related to each other, as when two brothers marry two sisters)
What is my godfathers niece to me