Rule 13 of CPC : Rule 13: Objections As To Non-Joinder Or Misjoinder

Explanation using Example

Imagine that Rita files a lawsuit against Sam and Alex for a breach of contract. However, she mistakenly does not include Tom, who is also a party to the contract and whose involvement is crucial to the case. Sam and Alex must raise the issue of nonjoinder (missing Tom in the lawsuit) at the earliest opportunity, typically at the beginning of the legal proceedings. If they wait until the court has already begun settling the issues, they may be considered to have waived their right to object to Tom's absence. If they do not raise this objection in time, the case might proceed without Tom, potentially affecting the fairness and outcome of the trial.