Having the same nightmare as others?? HELP!?

When i was a child i had the same nightmare over and over again that would scare me. I would be in a dark room and everything would gradually get louder then softer then louder then softer, then everything would begin to grow. It scared me when i was a child. However as ive gotten older i haven't had that dream anymore, however, i have met 3 other people who have had that same nightmare when they were a child. What does this mean? I just met them recently so i did not know them when i was a child. Is this just some weird coincidence or something more? help!!!