California Code, Family Code - FAM § 2330.1

In any proceeding for dissolution of marriage, for legal separation of the parties, or for the support of children, the petition or complaint may list children born before the marriage to the same parties and, pursuant to the terms of the Uniform Parentage Act, a determination of paternity may be made in the action. In addition, a supplemental complaint may be filed, in any of those proceedings, pursuant to Section 464 of the Code of Civil Procedure, seeking a judgment or order of paternity or support for a child of the mother and father of the child whose paternity and support are already in issue before the court. A supplemental complaint for paternity or support of children may be filed without leave of court either before or after final judgment in the underlying action. Service of the supplemental summons and complaint shall be made in the manner provided for the initial service of a summons by this code.