If your sister or brother had a grandchild, and you were a woman, you would be a grand aunt to that grandchild. Some people say great aunt, instead of grand aunt.
He would be your grand nephew; you would be his great-aunt.
Yes, your grandfather's sister would be called by some your grand aunt and by others your great aunt.
The aunt of a great grand niece is her aunt - the sister of her mother or father. The great grand niece has a great grand aunt, or great grand uncle, who is the sibling of one of her great grandparents. In normal conversation, such a person would usually be called "Aunt," becasue adding all those "greats" and "grands" is cumbersome and would probably just make her feel old.
Your nephew's son would call you his great uncle or great aunt. Some would use the terms grand uncle or grand aunt.
Your great grandmother's sister is your great great aunt (or some would say, your great grand aunt).
She is your father's aunt and your great aunt. You would be her grand niece.
My ancestor She would be my grand-aunt (unless, of course, she were actually my grandmother). A grand-aunt is not technically an "ancestor", although I do rather like the recently coined expression "ancestral aunt".
Tía is aunt. Bistía is great aunt or grand aunt.
Your nephew's baby would be your grand-nephew or grand-niece. You would be their grand-uncle or grand-aunt.
Your grand niece's son is your great grand nephew, or, some would say, your great great nephew. You are his great grand aunt or great grand uncle, or, some would say, great great aunt or great great uncle.
you say call me great aunt not grand aunt
Once the baby is born, you are considered to be its grand aunt or grand uncle.