California Code, Probate Code - PROB § 2203

(a) If proceedings for the guardianship or conservatorship of the estate are commenced in more than one county, the guardianship or conservatorship of the estate first granted, including a temporary guardianship or conservatorship of the estate, governs and extends to all the property of the ward or conservatee within this state and the other proceeding shall be dismissed.

(b) If proceedings for the guardianship or conservatorship of the person are commenced in more than one county, the guardianship or conservatorship of the person first granted, including a temporary guardianship or conservatorship of the person, governs and the other proceeding shall be dismissed.

(c) If a proceeding for the guardianship or conservatorship of the person is commenced in one county and a proceeding for the guardianship or conservatorship of the estate is commenced in a different county, the court first granting the guardianship or conservatorship, whether of the person or of the estate, may find that it is in the best interests of the ward or conservatee that the guardianship or conservatorship of both the person and the estate be maintained in that county or in such other county as the court shall determine. Thereupon, the guardianship or conservatorship proceeding in the court of the county found by the court to be in the best interests of the ward or conservatee shall govern and shall extend to all property of the ward or conservatee within this state, and the other proceeding shall be dismissed.