Except you forget about the existence of great aunts and great uncles. Then, those aunts and uncles would be cousins. It makes more sense to group all cousins together, since they are all members of the same extended family, yes?
No. Great aunts/uncles are not your cousins.
They are your great aunts/uncles.
Your Great Aunt is your parents Aunt.
Your cousin is
only ever the child of your parents sibling, or the child of your grandparents sibling, or the child of your great-grandparents sibling, etc, etc...
The number of your cousin depends on how far back your shared grandparent is.
First cousin means you both share a grandparent - 1 generation ago. Your parents' parent.
Second cousin means you both share a great grandparent - 2 generations ago. Your grandparents' parent.
Third cousin means you both share a great great grandparent - 3 generations ago. Your great grandparent's parent.
Degrees of removal count the generation of children below that type of child. Meaning your first cousins child is your First Cousin, Once Removed. Their child is your First Cousin, Twice Removed
Your Aunt, your Great Aunt, you Great Great Aunt, are your parent/grandparent/great grandparents sibling. THEY ARE NOT their siblings child!
Therefore they cannot be your cousin, unless via inbreeding, or because your maternal/paternal families are married together twice.
Poll