Formal:
* 細佬 (sai3 lou2): This is the most common and formal way to say "little brother."
* 細弟 (sai3 dai6): This is a slightly more formal and polite term, often used when referring to someone younger in a respectful manner.
Informal:
* 細佬仔 (sai3 lou2 zai2): This is a more informal and endearing way to say "little brother." It's often used by older siblings or close friends.
* 細佬 (sai3 lou2): This informal version can be used in close family settings.
Other options:
* 細佬 (sai3 lou2) /細妹 (sai3 mui6): These terms can be used in both formal and informal contexts, but they are more common among family members.
Note: The tones are written using Cantonese Romanization (Jyutping).
You can choose the appropriate term based on the situation and your relationship with the person.