The first thing to understand is the definition of a narrative essay. To put it quite simply this is the telling of the story. You're not there to argue a case for a particular point of view.
Remember the story has to be interesting. It needs to be logical and one of the most common formats in writing a narrative essay is to do so in chronological order. Who is the main character or characters in your story? What happens to them?
In this particular case you are asked to write a narrative essay about a broken family. Before you begin you will need to decide whether you're going to base this on a situation you know from personal experience or one you have discovered through your research. If you are basing it on a personal experience, you will need to disguise the people involved in the situation. Whichever path you take, it's highly advisable that you consult with your teacher or tutor beforehand so as to sort out both the topic and the approach you take.
Here are some elementary tips which are designed to help you write a narrative essay.
A narrative essay does not need a string of technical words or language. Keep it simple and keep it real. Likewise it is important that you stick solely to the facts and the action thereof. Get rid of any superfluous descriptions. Once you know the storyline, tell it in as few words as possible.
Because you are telling the story, you will have more impact upon the reader if you tell it from your point of view. Don't be an observer of this action but rather somebody who is directly involved in it.
It is never effective if you take the point of view of a commentator or a reporter who has witnessed something, as opposed to someone who was part of the action. Think of yourself as a storyteller rather than an essay writer.
You are not there to preach a sermon or make a political point. The quality of your writing in telling the story should be sufficient to make people think.