since my mom brother is considered my uncle..what about his wife? do i call her aunt?
Technically she's your Aunt through marriage. You don't have to call her Aunt, though. Small children call Uncle's wives and Aunty's husbands Aunt and Uncle because children don't call adults by their first name. But given your age, I'd just call her by her first name, what the other adults call her. It really depends on what you're comfortable with and how your family does things.
She is your Aunt, but only by marriage