Here's the breakdown:
* la esposa de mi tio: This literally means "the wife of my uncle".
* es Tia: This means "is aunt".
The issue is that "Tia" can refer to:
* Your aunt (by blood or marriage): The sister of your parent or the wife of your uncle.
* The wife of your uncle: This is the meaning used in the first part of the statement.
Therefore, the statement is redundant. It's saying the same thing twice:
* The wife of my uncle is my aunt.
A more concise way to say this would be:
* Mi tía es la esposa de mi tío. (My aunt is the wife of my uncle.)