California Code, Family Code - FAM § 17408

(a) Notwithstanding Section 17404, upon noticed motion of the local child support agency, the superior court may consolidate or combine support or reimbursement arrearages owed by one obligor to one obligee in two or more court files into a single court file, or combine or consolidate two or more orders for current child support into a single court file. A motion to consolidate may be made by a local child support agency only if it is seeking to enforce the orders being consolidated. The motion shall be filed only in the court file the local child support agency is seeking to have designated as the primary file.

(b) Orders may be consolidated regardless of the nature of the underlying action, whether initiated under the Welfare and Institutions Code, this code, or another law. Orders for support shall not be consolidated unless the children involved have the same mother and father and venue is proper pursuant to Section 17400.

(c) Upon consolidation of orders, the court shall designate which court file the support orders are being consolidated into the primary file, and which court files are subordinate. Upon consolidation, the court shall order the local child support agency to file a notice in the subordinate court actions indicating the support orders in those actions were consolidated into the primary file. The notice shall state the date of the consolidation, the name of the court, and the primary file number.

(d) Upon consolidation of orders, the superior court shall not issue further orders pertaining to support in a subordinate court file; and all enforcement and modification of support orders shall occur in the primary court action.

(e) After consolidation of court orders, a single wage assignment for current support and arrearages may be issued when possible.