Your father's younger brother would be referred to as your "paternal uncle." The term "paternal" indicates that the uncle is related to you through your father's side of the family. This distinguishes him from your mother's brother, who would be known as your "maternal uncle."
You would call your husband's younger brother a brother-in-law.
In Hindi, you would call your father's younger brother "chacha."
In Malayalam, you call a younger brother "Chettan."
Your father's brother is your uncle.
You would refer to your younger brother's wife as "bhabhi" in Hindi.
uncle
uncle
Brother in-law
cousin
aunt
The wife of your brother (younger or older than you) is your sister-in-law.
little brother