My Father rented an apartment on a month to month agreement. His Drug addict brother moved himself and his "family" in. My father could not get rid of them and ran off and now the drug addict family will not move out. They are not even on the rental agreement. Do they have rights?

Who is the landlord? They have rights but the landlord does too. He can evict the uncle but also sue dad for back rent.

Is the rent being paid ? The dad is liable for all the rents, the dad should have evicted them if he was the person who rented the apartment.

But the Landlord will have to evict them,

If your father signed a lease, he is responsible for that lease until it expires.

How long the brother has lived there will depend on whether he has any rights. If the brother is paying the rent, the landlord may not care.