There is no specific term in the English language to describe a relationship between you and your nephew's wife. Most people would say you are not related. If you must use some phrase, the phrase "my nephew's wife" is probably the clearest and most direct.
Nephews are the sons of your brother or sister. Therefore nephews who are not brothers to each other are first cousins to each other.
Great nephew
He is their Uncle and they are nieces and nephews.
Second cousins.
Your brother's children would be your nieces and nephews.
Your brother-in-law's children are your nephews and nieces.
If it's your sister then your sister, if it's your brother's wife then you sister-in-law
The English language has no relationship name for the wife of your great niece or great nephew.
Your sister's husband is your children's uncle. They are his nieces and nephews.
Your borther-in-law is your grandchildren's great uncle. They are his great nieces and great nephews.
You do not have a niece-in-law. Some of your nieces and nephews are that because they are the children of your husband's siblings. They are your nieces and nephews and you and your husband together are their "aunt and uncle."
Your daughter is you great nephews great cousin if u live in Australia ,USA ,UK