I would disagree that a narrative essay requires telling a story in chronological order. This is an easy way to accomplish this task, but often, narrative essays use elements of story-telling (and creative writing) but as rule, are not required to be one story told in a chronological way.
My best advice for narrative essays is to use real life whereever possible. If you are not a twin yourself, certainly you know some. When I think of "terrible twins" I automatically imagine a worn out mother with twin pre-school boys. Your essay could simply be glimpses into such a parent's day.