Naming & renaming a child is an incident of "legal custody" (sorry, I didn't create these eejit terms). Once adjudicated the father of this child you'd have equal (re)naming rights which means that you two should reach agreement, or you'd need to file a Request for Order with the Family Court to obtain an order, to get this child renamed. The renaming would be accomplished administratively through the Cal. Dept. of Public Health. http://www.cdph.ca.gov/certlic/birthdeathmar/Pages/CorrectingorAmendingVitalRecords.aspx
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