I would not choose the family member as a dream sign, then. If you don't find yourself questioning the reality of your mom on a daily basis, then you probably won't do it in a dream.

On the other hand, if you find that you and your mom often show up in weird places, the fact that you are in a weird place WITH your mom could be a good dream sign. How long have you been journaling? I have found it is best for dream signs to sort of evolve organically. Let your dream practice show you what the good ones are.