Cal. Probate Code § 2204

(a) If a proceeding for the guardianship of the person of the minor is filed in one county and a custody or visitation proceeding has already been filed in one or more other counties, the following shall apply: (1) If the guardianship proceeding is filed in a county where the proposed ward and the proposed guardian have resided for six or more consecutive months immediately prior to the commencement of the proceeding, or, in the case of a minor less than six months of age, since the minor’s birth, the court in that county is the proper court to hear and determine the guardianship proceeding, unless that court determines that the best interests of the minor require that the proceeding be transferred to one of the other courts. A period of temporary absence no longer than 30 days from the county of the minor or the proposed guardian shall not be considered an interruption of the six-month period. (2) If the guardianship proceeding is filed in a county where the proposed ward and the proposed guardian have resided for less than six consecutive months immediately prior to the commencement of the proceeding, or, in the case of a minor less than six months of age, a period less than the minor’s life, the court shall transfer the case to one of the other courts, unless the court determines that the best interests of the minor require that the guardianship proceeding be maintained in the court where it was filed. (3) If a petitioner or respondent in a custody or visitation proceeding who is an authorized petitioner under Section 2212 petitions the court where the guardianship proceeding is filed for transfer of the guardianship proceeding to the court where the custody or visitation proceeding is on file at any time before the appointment of a guardian, including a temporary guardian, the provisions of this subdivision shall apply to the court’s determination of the petition for transfer. Except as provided in this paragraph, the petition for transfer shall be determined as provided in Sections 2212 to 2217, inclusive. (b) The following shall apply concerning communications between the courts: (1) The court where the guardianship proceeding is commenced shall communicate concerning the proceedings with each court where a custody or visitation proceeding is on file prior to making a determination authorized in subdivision (a), including a determination of a petition to transfer. (2) If a petitioner or respondent, who is authorized to petition to transfer under Section 2212, petitions the court where the guardianship proceeding is filed for transfer of the guardianship after the appointment of a guardian, including a temporary guardian, the court in the guardianship proceeding may communicate with each court where a custody or visitation proceeding is on file before determining the petition for transfer. (3) If the court in the guardianship proceeding appoints a guardian of the person of the minor, including a temporary guardian, the court shall transmit a copy of the order appointing a guardian to each court where a custody or visitation proceeding is on file, and each of those courts shall file the order in the case file for its custody or visitation proceeding. (4) The provisions of subdivisions (b) to (e), inclusive, of Section 3410 of the Family Code shall apply to communications between courts under this subdivision. (5) The Judicial Council shall, on or before January 1, 2013, adopt rules of court to implement the provisions of this subdivision. (c) For purposes of this section, “custody or visitation proceeding” means a proceeding described in Section 3021 of the Family Code that relates to the rights to custody or visitation of the minor under Part 2 (commencing with Section 3020) of Division 8 of the Family Code.