psychological answer: The moon as your origin represents isolation. The fact that you returned for your unborn sister could mean you are struggling with feelings related to that, and perhaps associate your isolation with the lack of having said sister (are you an only child?) Looking through your old house with your sister could likely represent yearning for a lost childhood that never was. Or I could be wrong, basing this off way too much limited information.
Theosophical/Metaphysical answer: Personally, I think that the most plausible understanding of dreams is the world without time. No boundaries exist, because our imagination is the limit of this world. However, imo, this doesn't make dreams any less real. When we get angry unnecessarily, our anger is still real, even if the perceived threat isn't. Similarly, dreams are real until we realize we are dreaming (and even then that's flexible, if you've experienced lucid dreaming at all). Our brain perceives them just as real as what we call "reality" even though reality is the same brain processing signals.
Then comes the idea that our consciousness is connected somehow. We're all sending out bio-electric impulses, signals, what have you. Theoretically, we could be latching on to these energies, which manifests in your subconscious dream state as these coincidental events, people, places, etc.
This is all just my opinion, I in no way have any accreditation for this. It's just stuff I'm interested in.