(a) A civil action based upon a cause of action in ejectment, may be brought against:
(1) the person actually occupying the premises claimed, either in person or by tenant; or
(2) both the claimant and his tenant, or other occupant claiming under him; or
(3) if the premises are not actually occupied, a person exercising acts of ownership thereon adversely to the plaintiff.
(b) Joint tenants shall sue jointly in ejectment, but tenants in common may sue either jointly or separately, and any number of tenants in common, less than the whole number entitled, may sue jointly in reference to their undivided interests.