Medium - Hard Riddle?

If all of your information is complete and none of your 6 aunts has any grandkids then your mother has the most living descendants. She has 2, 3 or 4 children (we can't pin it down any more specifically since we don't know your mother's birth order relative to her 3 sisters) plus 18 grandkids (your 18 nieces and nephews.) Since you have these nieces and nephews we know that you're not an only child (so your mother is not the last born) so your mother has at least 2 children and at least 20 living descendants and possibly as many as 22 if she's the first born.