Your father's niece is your 1st cousin.
You and your grandmother's great niece are second cousins.
She was his niece.
Niece
Yes, they're related. Shes his niece twice removed. Shes also related to his wife
She is his great niece
A paternal niece is a niece on the fathers side. For example:my dad's sisters's daughter is my paternal niece
Your father's niece is your first cousin, and her daughter is your first cousin, once removed.
Yes.
Your fathers brothers are your uncles. You are their nephew, or niece.
No. Your wife's niece is also your niece, but the husband of the niece is not related to you or to your wife.
Your sister-in-law's niece is not related to you because you have no ancestors in common. ----- The above answer is true, but by marriage, that niece would also be your niece or your own daughter. This is because your spouse is blood/sibling related to his/her sister (your sister-in-law).
Your daughter-in-law's niece and nephew would be considered your grandchildren's cousins. So, you would be their grandparent-in-law.
Your niece's husband's daughter is also your niece's daughter and therefore she is your great niece. You are her great aunt or great uncle, depending on your sex. If your niece's husband's daughter is from a previous marriage, and so not also your niece's daughter, you are not related to her. Of course, if your niece adopts her, then she is your adopted great niece. If your niece married her husband while his daughter was very young and everyone has been treating her as your niece's daughter, then you can call her your great niece if you want, but that does not change the fact that you have no common ancestors and therefore are not related to each other.
No
Your grandchild and your niece are first cousins, once removed.
Your niece and your daughter are first cousins to each other.
maybe