Here is an example of a woman who had a mutual dream with her ex-boyfriend. The dreams were not exactly the same, but there was definite overlap and they happened at the same time. For this one, I am sharing some of the question and answer process so you can see a dream session in action.

Amy sent in this dream:
2 nights ago, I had a dream in which I was running through a dark house being chased by my ex boyfriend. I ran in a room and tried to close the door and could not, and yelled out “What do you want from me?!” Just then a scary voice I said “I want you” I instantly woke up and experienced what I now know is sleep paralysis.  Less than a minute later my phone rang and it was my ex boyfriend! He apologize for the phone call at 2:30 a.m., however he said that he had to call me to be sure I was okay. He said he woke up from a dream that felt real, in which I was falling from a cliff and he was trying to grab me to save me, however I fell to my death.  What does this mean?
~Amy

Mimi:
Do you have a sense for what this dream means to you?

Amy:
I have absolutely no idea. I somewhat feel that I was wanting to get away from my ex boyfriend and move on, however him having the same dream or similar dream at the same time is what concerns me. I dreamed something was grabbing me and I was getting away, he dreamt that he was grabbing me and trying to save me at the same time.

Mimi:
What was going on in your life at the time you had this dream?:

Amy:
I recently broke up with my boyfriend about 2 months ago and moved into my own house he wants to get back together however I do not.

Mimi:
What was the main feeling in the dream? :
My dream was absolutely terrifying.

Mimi:
What you had was a shared or mutual dream with your ex. It is not uncommon amongst people who have emotional ties (couples, siblings, parent/child etc). Just because you had this experience does not mean you should get back together with him, it just means you guys still have an open line of mental communication. If you look at the energetic dynamic, in his dream he is saving you, in your dream you feel terrified, and you want to get away.  From what you have described, this reflects the actual dynamic between the two of you, where he wants to come after you but you want to get away. I am very pro-relationship in general, but the fact that you felt terrified is your own consciousness telling you how you really feel about him at the time of the dream.
Sometimes things seem ‘fine’ on the surface, but our dreams bring to light what is really going on underneath the surface. So I’m not saying this dream means never get back together with him, or that he is a bad person – after all, he was trying to save you in his dream…however your feelings are important to consider. Perhaps they were a reflection of how you felt in the moment, and that can change.  But the fact that you found the dream absolutely terrifying is of concern.
Listen to your instincts always about who to surround yourself with. I hope this helps.