Are you familiar with the term "Pandora's Box"?
It is a story about opening a box and the unknown things that come flying out.
If you "verbally" rented a room; you do not have a written contract.
How can it be "without the owner's knowledge"; sounds very suspicious.
If another "person moves in" you have no rights or privileges regarding that person,
Particularly in evicting them.
If you choose to stay in this predicament, you have to accept what came out of the "box".