Didi. 弟弟。The characters look like two little devils, don't they?
In Mandarin Chinese, you can call brother as "xiōng dì" (兄弟) if he is a younger brother, or as "gē gē" (哥哥) if he is an older brother.
In Malayalam, you call a younger brother "Chettan."
You would call your husband's younger brother a brother-in-law.
didi or 弟弟 is younger brother and in case you want to know gege or 哥哥 is older brother.
In Hindi, you would call your father's younger brother "chacha."
Brother in-law
The wife of your brother (younger or older than you) is your sister-in-law.
little brother
ni hao
tamma
Uncle
For 'older brother', the translation would be '哥哥' or in pinyin, 'ge ge'. The translation for 'younger brother' would be '弟弟' or 'di di'. To refer to 'brothers', you would call them your '兄弟' or 'xiong di'.