Legal Question in Personal Injury in California

Very sorry to hear of your dilemma, and I suggest you take the appropriate action as soon as possible. There are several issues going on here, so lets take each one on its own. You focused on protecting yourself, and so that's our focus.

First and foremost, document what has happened and report each and every incident to your local law enforcement asap.

The next step is to prevent your brother's ex-girlfriend (the "Ex"), from coming near you, your property, your children, and the places you go or they are to be found. It is unclear from your information whether your brother lives with you or not. If there has been abuse, he has a close enough relationship to seek a domestic violence restraining order, and extend it to the residents of his household.

If he does not live there, or if he was not himself abused, you should seek a civil restraining order against the Ex. The level of proof and the need to show an ongoing threat are higher than for a domestic violence order, but it appears you have enough to show the Ex is a continuing threat. Contact an attorney or seek self-help from the local superior court with documented incidents. You can at least get a temporary restraining order, pending a hearing in about two to four weeks.

Regarding posting fliers, calling others about the Ex's actions, or picketing her place of business, you need to show caution unless you find yourself on the other end of a complaint for defamation, harassment, or even as a defendant against a restraining order yourself. Even if you can eventually prove that everything you say is true, the behavior could still be seen as harassment, cause damage to her ability to earn a living, and in the end cost you a great deal of time and legal fees defending yourself.

Its best to seek the protections against the Ex and allow you and your family to return to your lives, unmolested.