You might think in terms of "two" just for the heck of it. I use to have "pairs" of dreams about my mother/stepmother when I was in therapy, working on issues related to them. If you dreamed about one ex that might be about that ex but seems you are dreaming about ex's in general but two of them. Were they alike in some way or have different/opposite aspects to show you about some other problem you are currently working on?