California Code, Labor Code - LAB § 5408

If an injured employee or, in the case ofthe employee's death, any ofthe employee's dependents, is under 18 years of age or incompetent at any time when any right or privilege accrues to such employee or dependent under this division, a guardian or conservator of the estate appointed by the court, or a guardian ad litem or trustee appointed by the appeals board, may, on behalf of the employee or dependent, claim and exercise any right or privilege with the same force and effect as if no disability existed.

No limitation of time provided by this division shall run against any person under 18 years of age or any incompetent unless and until a guardian or conservator of the estate or trustee is appointed.  The appeals board may determine the fact of the minority or incompetency of any injured employee and may appoint a trustee to receive and disburse compensation payments for the benefit of such minor or incompetent and his family.