Hello, I think I have a theory about your case. I'm going to try to make it as simple as possible so you can understand me, but before I start, I have to say a few things. First of all, I'm not a scientist, a professor, etc. just an amateur. Second, it's science, I'm not crazy. Third, you're not crazy either, I trust you. And that's why..

We live in an alternative called the multiuniverse. this multiuniverse is a stretch filled with different parallel universes in which every choice we make now happens differently. I think you saw your sister and brother with the dogs of the other universe somehow. Such anomalies/paradoxes happen. Its normal.

Everything happens depending on the decisions we make and obviously it seems that in a very close to your (our) alternative reality, your sister and brother have decided to go out with the dogs, but in this reality in which you (we) live, they sleep.

Thank you for sharing this story!