Cal. PROB § 21620

Except as provided in Section 21621, if a decedent fails to provide in a testamentary instrument for a child of decedent born or adopted after the execution of all of the decedent’s testamentary instruments, the omitted child shall receive a share in the decedent’s estate equal in value to that which the child would have received if the decedent had died without having executed any testamentary instrument.