Legal Question in Family Law in California

Probably not. There is a presumption that the child born of a marriage, where the parties are cohabiting, is the child of the marriage. This presumption is subject to defeat by genetic testing, but the genetic testing must be done within two (2) years of the birth of the child. There is case law that states that this presumption will not be used in situations where the man has an affair with a married woman, but that situation involves the outside man trying to get out of his responsiblities for the child when the husband was vacant. After 15 years, I doubt a court would assist you, as your child has most likely established a bond with the mother's husband. The policy in this state is not to disturb that bond.