Your tenancy is valid because your landlord, who is the mesne tenant, created a tenancy - your subtenancy. This brings about a relationship of landlord and tenant between you and them.

The original lease specified that any subtenancy must be approved, but my father was never approached. Isn’t this an unauthorized subtenancy — which allows me to terminate the underlying lease?

A: It depends on how the new tenancy was created. If the property owners created a subtenancy for the new tenants under your existing lease, then you may still be liable for the rent. In this case ...