Cal. Family Code § 7601

(a) “Natural parent” as used in this code means a nonadoptive parent established under this part, whether biologically related to the child or not. (b) “Parent and child relationship” as used in this part means the legal relationship existing between a child and the child’s natural or adoptive parents incident to which the law confers or imposes rights, privileges, duties, and obligations. The term includes the mother and child relationship and the father and child relationship. (c) This part does not preclude a finding that a child has a parent and child relationship with more than two parents. (d) For purposes of state law, administrative regulations, court rules, government policies, common law, and any other provision or source of law governing the rights, protections, benefits, responsibilities, obligations, and duties of parents, any reference to two parents shall be interpreted to apply to every parent of a child where that child has been found to have more than two parents under this part.