Persons having claims against the plaintiff may be joined as defendants and required to interplead when their claims are such that the plaintiff is or may be exposed to double or multiple liability. It is not ground for objecting to the joinder that the claims of the several claimants or the titles on which their claims depend do not have a common origin or are not identical but are adverse to and independent of one another, or that the plaintiff avers that he is not liable in whole or in part to any or all of the claimants. A defendant exposed to similar liability may obtain such interpleader by way of cross-claim or counterclaim. The provisions of this rule supplement and do not in any way limit the joinder of parties permitted in Rule 20.