Yes, or you can call them siblings
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.
The relationship of the sibling of your sister-in-law or brother-in-law to you does not have a name in English. You could call them your brother- or sister-in-law if you want, or you can call them the brother or sister of your brother- or sister-in-law.
Your brother or sister's daughter is your niece.
Yes, she had a mother, father and a brother and sister.
Your brother would call your husbands sister by her first name. Or, "my (sibling's) sister in law.
I don know about thisccxxxsaaasfgbnnnnnbdhsfjsgjfnfnndgjhbkdhkdgizghcvggfffdsdfgggdndgdjcmdjchfvnvgdkdygjtgb
She will be referred to as the sister of someone's brother-in-law.
Your sister-in-law is either the sister of your spouse or the wife of your brother. In either case, she would call you her brother-in-law.
You call him your nephew. (pronouced nes-few)
you call him your brother in law
Your brother's wife is your sister-in-law.
You would call your sister's husband your brother-in-law.