Do you know if he enabled mac address filtering on it? It sounds like this is an existing network that you had already? If so he may have limited the "mac addresses" that can connect.
If you know how to enable SID broadcast then you are part way there - can you see an option around there for mac address filtering? If so you need to add your mac address (of your laptop) to the list if this option is enabled.
Your bro may have secured it using a secure key in which case you'll really need to know that. Might sound daft and i'm sure you can't otherwise you wouldn't be here, but can't you speak to your bro?