Sounds like there's another child out there. The DA files when a child is on state aid. He may have been excluded, if this is not recent.
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Based on the facts above there is nothing to indicate a paternity test is requested. The Petition in child support proceedings that are brought by the Child Support Services (CSS), if outside of an already filed dissolution, are based upon the filing of the Petition pursuant to family code 7630, et seq. The reference you wre seeing to "complaint DA-Paternity" may have been in reference to the FL-200 Form (http://www.courts.ca.gov/documents/fl200.pdf) used in this situation by child support services. To quell your worries you should call the worker assigned to the case.
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Assuming there is no other type of related case, for example a dissolution, then the County files a complaint to establish the legal relationship between the parent and child. That legal relationship needs to be established in order to enforce the obligation to pay child support. Paternity isn't really the issue, if the kids were born during marriage a presumption of paternity applies under Family Code 7611.