question about shared dreams

I'm wondering if a person has to be in your dream when you have a shared dream with them. I had a dream that I was in mcdonalds with a weird floating blob man thing. Anyway, he was trying to kidnap me, but he bought me an ice cream cone first. While he was buying it for me i ran into the bushes outside and saw someone drive past and I jumped on the back of the car to get away. My cousin had that same dream, we even drew the blob man to see if we both really dreamt the same thing and they looked exactly alike. but my cousin wasn't in my dream and I wasn't in hers. and the blob in her dream was black and in mine he was blue. Also the cars were different. I jumped on the back of a black suburban and she jumped on the back of a white mitsubishi. I'm wondering if this is a shared dream or just a coincidence. I'd like to hear any suggestions or thoughts