Cal. CCP § 397.5

In any proceeding under the Family Code where it appears that both petitioner and respondent have moved from the county rendering the order, the court may, when the ends of justice and the convenience of the parties would be promoted by the change, order that the proceedings be transferred to the county of residence of either party. In any proceeding in which there is a concurrent action or proceeding under Division 17 (commencing with Section 17000) of the Family Code involving the local child support agency, the court may transfer venue under this section for any action or proceeding not subject to Division 17 (commencing with Section 17000) of the Family Code, but shall redirect any motion pursuant to this section to the court of competent jurisdiction under Section 4251 of the Family Code for change of venue in those actions and proceedings subject to Division 17 (commencing with Section 17000) of the Family Code. The decision on any motion redirected pursuant to the preceding sentence shall apply only to the action or proceeding under Division 17 (commencing with Section 17000) of the Family Code and shall be at the sole discretion of the court of competent jurisdiction hearing the action or proceeding pursuant to Section 4251 of the Family Code.