Great great aunt/uncle.
To your niece, you are the aunt/uncle, to her child you would be the great aunt/uncle.
So you would then be the great great aunt/uncle of her child's child (her grandson)
Your grandson and your niece are first cousins once removed.
Your niece and your grandson are First cousins, Once Removed.
Your grand niece and your grandson are second cousins to each other
Your niece and one of your grandson's parents are first cousins. That makes your niece a first cousin once removed of your grandson.
Your great niece and your great grandson are second cousins, once removed.
A great niece and a grandson of the same person are second cousins to each other.
Your great grandson and your husband's great niece are second cousins, once removed.
Your grandson and your great great niece are second cousins, once removed, to each other
Your wife's niece is also your niece, so you are her uncle.
There is no relation between you and your grandmother's cousin-in-law's grandson.
Your sister's husband is your brother-in-law. His niece is a child of one of his siblings, and is also a niece of your sister by marriage. There is no relation to you.
Could be your daughter or your niece.
Your son and your niece are first cousins.
Your father's great grandson could be your grandson, or your great nephew.
He is your grandson by marriage or grandson in-law.
Nothing. Your niece in law. Your brother in laws niece.
Your Aunt's niece is you (if you are female), your sister, or your First Cousin.
Your brother's granddaughter is your grand niece or great niece.
You and your uncle's grandson are first cousins once removed.
Your grandson is your sister's great nephew and she is his great aunt.
Your nephew is not related to your husband's niece. However, your nephew is also your husband's nephew and his niece is also your niece.
You grandson is great great nephew to your uncle. You uncle is great great uncle to your grandson
Your niece is the daughter of your sister or brother. You are her Aunt (if you are female) or her Uncle (if you are male).
that would be your niece or if you want to be fussy then your niece in law!