This summary is not the rule. The rule text controls.
If someone sues the wrong people, or too many people, or leaves someone out, the case doesn't get thrown out just because of that mistake. Courts understand these mix-ups happen, and there's an easy fix instead of starting over.
The judge has the power to add people to the case or remove them, even without anyone asking. This can happen at any point while the case is going on. The judge just has to make sure it's done fairly to everyone involved.
The judge can also split up claims so that different issues involving different people are handled separately. This helps keep the case organized when there are multiple parties or claims that don't need to be decided together. The main point of this rule is to keep cases moving forward and focused on the real issues, instead of getting stuck on technical problems about who is included in the lawsuit.
