You are the nephew if you are male and a niece if you are female.
Aunt's
Tom Sawyer's aunt was Aunt Polly.
Great aunt.
Your great aunt.
Aunt
Your aunt is your daughter's great aunt. Your daughter is your aunt's great niece.
Capitalize "Aunt" when it is used as a proper noun directly before the person's name, such as "Aunt Jane," "Aunt Mary," or "Aunt Sarah." However, if the word "aunt" is used informally or generically, it is not capitalized, such as "my aunt" or "she is an aunt."
If the dad's sister's aunt is also your dad's aunt, then your dad's aunt is your great aunt. However if she is not your dad's aunt, then she is your aunt's aunt and not necessarily related to you.
Your Aunt is your children's Great Aunt.
Your father's aunt is your great aunt.
Your father's aunt is your great aunt.
Your father's aunt is your great aunt.