Your father-in-law's sister is your spouse's aunt but is not related to her. Call her by her name.
Your sister's husband is your father's son-in-law.
The sons of your father's sister are your first cousins.
Your father's sister is your, paternal aunt,and your mother's sister is your, maternal aunt.Father's sister is your aunt.
Your father's sister's son (or daughter) is your first cousin.
'Aunt' More informally, she may be called 'Aunty ****'
She is your aunt.
You don't call your brother's sister your aunt. Your brother's sister is your sister, or you. Your aunt is the sister of your mother or father.
An Aunt.
AUNT
Cousin
your aunt.(: