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)
You are a great great Aunt (or Uncle) to the grandson of your Nephew.
Your niece's son is your great nephew. You are his great aunt or great uncle.
She is your Great Aunt or your Grandmother.Breaking it down, your father's uncle is your great uncle. Your great uncle's brother is also your great uncle (or your grandfather), and his sister is your great Aunt (or grandmother).
To your uncle, you are his niece or nephew.
She is your Great Aunt in law!
She is your Great Aunt or your Grandmother.Breaking it down, your father's uncle is your great uncle. Your great uncle's brother is also your great uncle (or your grandfather), and his sister is your great Aunt (or grandmother).
You would be his Great Uncle or Great Aunt He in turn would be your Great Nephew.
You are her great-aunt/uncle. She is your great-niece.
grandparentGreat Aunt or Great Uncle
Your aunt's great uncle is also your parent's great uncle. So 2Great Uncle would be one way of naming them.
A niece or nephew is the child of an aunt's or uncle's brother or sister. So the parents of the aunt/uncle and of the niece's/nephew's parents are the same people - their grandparents. The grandmother of the aunt or uncle is the great grandparent of the niece or nephew.