You would call your husband's younger brother a brother-in-law.
You call your husband's senior brother simply a brother in-law. There is no difference whether he is a senior brother or a younger brother he remains your brother in-law.
In Malayalam, you call a younger brother "Chettan."
Your brother would call your husbands sister by her first name. Or, "my (sibling's) sister in law.
The word for brother in Tamil is "சகோதரன்" (sakodharan).
brother in law
Brother in-law
The wife of your brother (younger or older than you) is your sister-in-law.
Sister-in-Law
little brother
Uncle
tamma
Younger brother in Hindi is called "छोटा भाई" (chhota bhai).