Great Aunt ??

I was talking to my nephew yesterday on Facebook and he keeps reminding me that I am going to be a great aunt in 41 one days, I told him to stop calling me that, makes me feel old, I said Great Aunts are 70-80 year olds and I am only 18.  Elliott said but you have been 18 for over 20 years now, I said no 30 years haha.