Legal Question in Civil Litigation in California

It's not that simple. Often yes but not always. If they are indisputably jointly liable for the damages, the plaintiff can sue one, some or all, and if less than all it is up to the defendants who are sued to cross-complain against the left out parties for indemnity and contribution. Sometimes, though, different people are solely responsible for specific parts of the damages. In that case if the plaintiff doesn't sue them all, the plaintiff cannot get a judgment for all their damages.