I have done a lot of memoir writing. In fact, a majority of my Chicken Soup stories are memoirs. I nearly always submit the stories to my critique group, and it's a good thing I do.
One of the biggest problems with memoir writing is that I remember the incident and all the things about it plainly. I knew the people involved, their characteristics and actions, but the reader does not. So, they are often left with questions or wanting to know more about a character or a situation.
Recently, I submittted a story about my grandparents, who had lived separated for many years. When my grandfather was dying of cancer, my grandmother made a trip to his town to take care of him in the final weeks of his life. In the story, I mention a landlady at the rooming house where he lived. One of the critiquers wanted to know if she was "the other woman." --the one who caused their marriage to break-up. I can see where a reader might be looking for that kind of explanation. In reality, the split happened probably twenty years earlier and the landlady was only there to collect the monthly rent and say a hello now and then.
To go back and explain all that would only add more than needed to thiis particular story. It might be a full story on its own. There were a couple other questions from the critiquers, too. They questioned reasons behind things that had happened. As the writer of the story, I need to decide what of those things they asked about are important enough to be addressed. Or are any of them that important to the story itself? Would adding several more parts to the story detract from the original intent?
If you are working on a memoir story, try to read it with objective eyes. Ask yourself what else might be necessary in order to clarify the story itself. But I would add that you need to be wary of adding too much detail. There's a fine line between too little and too much. With practice, you'll learn where to draw it.