Parties to a suit in equity are, in general, more numerous than in a suit at law. At common law only two adverse interests can be adjudicated in the same case. While there may be an indefinite number of plaintiffs or of defendants, all the plaintiffs and all the defendants must have a joint or common interest. In a suit in equity any number of mutually adverse interests may be adjudicated in the same suit.

The result of this is, that in a suit in equity the complainant must often join as defendants, not only those parties against whom he seeks relief but also other persons having an interest in the subject matter of the suit.