He would be your brother-in-law
You would refer to your younger brother's wife as "bhabhi" in Hindi.
In the English language there is no difference between the wife of an elder brother and the wife of a younger brother or of a twin brother. The wife of any brother is your sister-in-law. If you are actually talking to her, however you should just call her by her name. Nicknames are fine too.
In English, the wife of your brother (elder or younger) is your sister-in-law. If you have a child, she is your child's aunt.
The wife of your brother (younger or older than you) is your sister-in-law.
Your younger brother's wife's sister's daughter would be your son's cousin.
A hoe.
Brother in-law
aunt
Your brother's wife is your sister-in-law.
younger brother's wife -- maradalu elder brother's wife ---vadina
We call "Mami" to moms brother's wife.
She is your aunt. This is true in most traditions. English does not distinguish between an aunt by marriage (father's brother's wife) or an aunt by blood relation (father's sister).