No, our solar system isn't the only one.
Step-by-step explanation:
There are many other solar systems deep in space, waiting to be discovered.
The universe is big, it's impossible that our solar system isn't the only one.
Considering the fact we have milkyways, etc. We haven't gone outside if our solar system so, we might not be able to reach any other solar system quite yet.
There are endless possibilities out there.