CCP §378: (a) All persons may join in one action as plaintiffs if: (1) They assert any right to relief jointly, severally, or in the alternative, in respect of or arising out of the same transaction, occurrence

(a) All persons may join in one action as plaintiffs if: (1) They assert any right to relief jointly, severally, or in the alternative, in respect of or arising out of the same transaction, occurrence, or series of transactions or occurrences and if any question of law or fact common to all these persons will arise in the action; or (2) They have a claim, right, or interest adverse to the defendant in the property or controversy which is the subject of the action. (b) It is not necessary that each plaintiff be interested as to every cause of action or as to all relief prayed for. Judgment may be given for one or more of the plaintiffs according to their respective right to relief.