Everything you tell your attorney about your case is considered to be confidential. This is known as the attorney-client privilege, and it goes into effect once an attorney agrees to represent you.
Under state laws, your attorney cannot disclose this confidential information without your permission. This rule does not protect what you tell to others. So if you say the same things about your case to your brother and to your lawyer, your brother could be forced to reveal it in court proceedings. Your lawyer couldn’t.
The point of this legal rule is to encourage you to be honest when communicating with your attorney. Remember that your lawyer cannot represent you effectively without full knowledge of the facts.