Short answer. Yes. The Rules of Court permit all persons whose claims arise out of the same transaction or series of transactions to join as plaintiffs in one complaint, provided a question of law or fact common to all of them arises in the action. Joinder is permissive — an option, not an obligation.
What the law says
All persons in whom or against whom any right to relief in respect to or arising out of the same transaction or series of transactions is alleged to exist, whether jointly, severally, or in the alternative, may, except as otherwise provided in these Rules, join as plaintiffs or be joined as defendants in one complaint
Rule 3, Section 6 — Permissive joinder of parties. Read the full provision →
The two requirements
Permissive joinder rests on two conditions, and both must be met. First, each person's right to relief must arise out of the same transaction or series of transactions — the same botched sale, the same collapsed building, the same fraudulent scheme run on many investors. Second, there must be a question of law or fact common to all such plaintiffs that will arise in the action. Victims of entirely separate wrongs cannot bundle their claims into one case merely because the defendant is the same person; what unites the plaintiffs must be the transaction and a shared question, not convenience alone.
"May", not "must"
The operative word in the rule is may. Joining is a choice each wronged person makes; nobody is compelled to sue alongside the others, and a victim who prefers a separate case keeps that right. The rule also works in both directions — the same test governs joining several plaintiffs and impleading several defendants, whether jointly, severally, or in the alternative. In practice, joining makes sense when the evidence is largely shared: one set of documents, one set of witnesses, one filing instead of many, and no risk of different courts reaching inconsistent findings on the same facts.
The court keeps control
Joinder is not a licence to entangle strangers in each other's disputes. The rule itself gives the court a corrective power: it may make such orders as may be just to prevent any plaintiff or defendant from being embarrassed or put to expense in connection with any proceedings in which he may have no interest. So if some joined claims drift into matters that concern only some of the parties, the court can separate the proceedings or shape the trial so nobody is dragged through litigation that has nothing to do with them. Joining first and sorting the details out under the court's supervision is how the rule is designed to work.
Deciding whether to join
Before signing on to a joint complaint, compare your claim with the others'. Do you rely on the same contract, the same incident, the same misrepresentation? Will the same witnesses prove your loss and theirs? If yes, joinder usually saves money and strengthens the case's coherence. If your situation differs materially — a different date, a different agreement, a different defence likely to be raised against you alone — a separate suit may serve you better. Note that joinder of specific, individually-owned claims is different from a class suit, which has its own stricter requisites; a lawyer can tell you which vehicle fits your group.