California Code, Probate Code - PROB § 222

(a) If property is so disposed of that the right of a beneficiary to succeed to any interest in the property is conditional upon surviving another person and it cannot be established by clear and convincing evidence that the beneficiary survived the other person, the beneficiary is deemed not to have survived the other person.

(b) If property is so disposed of that one of two or more beneficiaries would have been entitled to the property if he or she had survived the others, and it cannot be established by clear and convincing evidence that any beneficiary survived any other beneficiary, the property shall be divided into as many equal portions as there are beneficiaries and the portion of each beneficiary shall be administered or distributed, or otherwise dealt with, as if that beneficiary had survived the other beneficiaries.