Please see the following probate code (explanation below):
2205. (a) Except as provided in Section 304 of the Welfare and Institutions Code, and subject to the provisions specified in subdivision (b), upon the filing of an order appointing a guardian of the person of a minor in a guardianship proceeding, including an order appointing a temporary guardian of the person of the minor, the court in the guardianship proceeding shall have exclusive jurisdiction to determine all issues of custody or visitation of the minor until the guardianship proceeding is terminated. (b) This section is subject to the provisions of Sections 1510 of this code, and 8714, 8714.5, and 8802 of the Family Code, relating to consolidation of guardianship and adoption proceedings and the court where the consolidated case is to be heard and decided.
So this code gives jurisdiction over all custody and visitation issues to the probate court; as such, the family court lacks jurisdiction. A motion to dismiss can be filed if the parent does file a visitation suit in family court.
That code is available here:http://www.leginfo.ca.gov/cgi-bin/displaycode?section=prob&group=02001-03000&file=2200-2205
Another option, if nothing has yet been filed, is to provide the above statute to the parent seeking visitation, along with a letter stating that the proper court is probate, and should the parent file improperly in family court, the guardian will request attorney fees and costs, in order to get a dismissal, pursuant to family code 271, below:
271. (a) Notwithstanding any other provision of this code, the court may base an award of attorney's fees and costs on the extent to which the conduct of each party or attorney furthers or frustrates the policy of the law to promote settlement of litigation and, where possible, to reduce the cost of litigation by encouraging cooperation between the parties and attorneys. An award of attorney's fees and costs pursuant to this section is in the nature of a sanction. In making an award pursuant to this section, the court shall take into consideration all evidence concerning the parties' incomes, assets, and liabilities. The court shall not impose a sanction pursuant to this section that imposes an unreasonable financial burden on the party against whom the sanction is imposed. In order to obtain an award under this section, the party requesting an award of attorney's fees and costs is not required to demonstrate any financial need for the award. (b) An award of attorney's fees and costs as a sanction pursuant to this section shall be imposed only after notice to the party against whom the sanction is proposed to be imposed and opportunity for that party to be heard. (c) An award of attorney's fees and costs as a sanction pursuant to this section is payable only from the property or income of the party against whom the sanction is imposed, except that the award may be against the sanctioned party's share of the community property.
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